Simple Machines

15 questions

Question 1Question

A screw jack with a thread pitch of 0.5 cm0.5\text{ cm} is operated using a Tommy bar of length 35 cm35\text{ cm}. If the machine has an efficiency of 40%40\%, what is the minimum effort force required to raise a load of mass 880 kg880\text{ kg}? (Take g=10 m/s2g = 10\text{ m/s}^2 and π=227\pi = \frac{22}{7})

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Answer: 50 N50\text{ N}

Answer

The minimum effort force required is 50 N50\text{ N}.
The effort distance per turn is the circumference 2πr=2×227×35 cm=220 cm2\pi r = 2 \times \frac{22}{7} \times 35\text{ cm} = 220\text{ cm}. Dividing by the pitch (0.5 cm0.5\text{ cm}) yields a Velocity Ratio of 440440. Applying the 40%40\% efficiency gives a Mechanical Advantage of MA=0.40×440=176\text{MA} = 0.40 \times 440 = 176. Finally, dividing the load force (8800 N8800\text{ N}) by MA\text{MA} gives an effort force of 50 N50\text{ N}.

Step-by-Step Solution

1
Calculate the total load force in Newtons
L=mg=880 kg×10 m/s2=8800 NL = m \cdot g = 880\text{ kg} \times 10\text{ m/s}^2 = 8800\text{ N}
Effort overcomes weight force, which is mass multiplied by gravitational acceleration.
2
Calculate the Velocity Ratio (VR) of the screw jack
VR=2πrp=2×227×35 cm0.5 cm=220 cm0.5 cm=440\text{VR} = \frac{2 \pi r}{p} = \frac{2 \times \frac{22}{7} \times 35\text{ cm}}{0.5\text{ cm}} = \frac{220\text{ cm}}{0.5\text{ cm}} = 440
The effort travels around the circumference of a circle of radius rr, while the load moves vertically by one pitch length pp per revolution.
3
Determine the Mechanical Advantage (MA) from efficiency
MA=η×VR=0.40×440=176\text{MA} = \eta \times \text{VR} = 0.40 \times 440 = 176
Efficiency is defined as η=MAVR\eta = \frac{\text{MA}}{\text{VR}}, so MA=ηVR\text{MA} = \eta \cdot \text{VR}.
4
Calculate the effort force E
E=LMA=8800 N176=50 NE = \frac{L}{\text{MA}} = \frac{8800\text{ N}}{176} = 50\text{ N}
Mechanical advantage is the ratio of load to effort force (MA=LE)(\text{MA} = \frac{L}{E}).

Key Concept

Relationship between Velocity Ratio, Mechanical Advantage, Efficiency, and Pitch in a Screw Jack
Question 2Question

An inclined plane of length 5 m5\text{ m} is used to lift a load of 400 N400\text{ N} through a vertical height of 1 m1\text{ m}. If an effort of 100 N100\text{ N} is applied parallel to the incline, what is the efficiency of the machine?

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Answer: 80%80\%

Answer

The efficiency of the machine is 80%80\%.
The correct answer of 80%80\% is obtained by finding the velocity ratio (distance moved by effort divided by distance moved by load, 5/1=55 / 1 = 5) and the mechanical advantage (load divided by effort, 400/100=4400 / 100 = 4), then calculating efficiency as (MA/VR)×100%=(4/5)×100%=80%(\text{MA} / \text{VR}) \times 100\% = (4 / 5) \times 100\% = 80\%.

Step-by-Step Solution

1
Calculate the Velocity Ratio (VR) of the inclined plane
VR=Length of inclineHeight=5 m1 m=5\text{VR} = \frac{\text{Length of incline}}{\text{Height}} = \frac{5\text{ m}}{1\text{ m}} = 5
Velocity Ratio is the distance moved by the effort divided by the distance moved by the load.
2
Calculate the Mechanical Advantage (MA)
MA=LoadEffort=400 N100 N=4\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{400\text{ N}}{100\text{ N}} = 4
Mechanical Advantage measures how many times a machine multiplies the applied force.
3
Calculate the Efficiency
Efficiency=(MAVR)×100%=(45)×100%=80%\text{Efficiency} = \left(\frac{\text{MA}}{\text{VR}}\right) \times 100\% = \left(\frac{4}{5}\right) \times 100\% = 80\%
Efficiency is defined as the ratio of Mechanical Advantage to Velocity Ratio expressed as a percentage.

Key Concept

Efficiency of Simple Machines (Inclined Plane)
Estimated Time:45s
Question 3Question

A wheel and axle machine having a wheel radius of 25 cm25\text{ cm} and an axle radius of 5 cm5\text{ cm} is used to raise a load of mass 80 kg80\text{ kg} vertically through a height of 10 m10\text{ m}. If the efficiency of the machine is 80%80\%, what is the work done against friction during this operation? (Take g=10 m s2g = 10\text{ m s}^{-2})

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Answer: 2,000 J2,000\text{ J}

Answer

2,000 J2,000\text{ J}
The useful work done on the load is Wout=mgh=80×10×10=8000 JW_{\text{out}} = mgh = 80 \times 10 \times 10 = 8000\text{ J}. Since efficiency is 80%80\%, the total work input required is Win=80000.80=10,000 JW_{\text{in}} = \frac{8000}{0.80} = 10,000\text{ J}. Therefore, the work lost to friction is WinWout=10,000 J8,000 J=2,000 JW_{\text{in}} - W_{\text{out}} = 10,000\text{ J} - 8,000\text{ J} = 2,000\text{ J}.

Step-by-Step Solution

1
Calculate the useful work output of the machine
Wout=mgh=80 kg×10 m s2×10 m=8,000 JW_{\text{out}} = mgh = 80\text{ kg} \times 10\text{ m s}^{-2} \times 10\text{ m} = 8,000\text{ J}
Useful work output is the gravitational potential energy gained by raising the load.
2
Calculate the total work input using the efficiency equation
Win=WoutEfficiency=8,000 J0.80=10,000 JW_{\text{in}} = \frac{W_{\text{out}}}{\text{Efficiency}} = \frac{8,000\text{ J}}{0.80} = 10,000\text{ J}
Efficiency is defined as Work OutputWork Input\frac{\text{Work Output}}{\text{Work Input}}, so Work Input = Work OutputEfficiency\frac{\text{Work Output}}{\text{Efficiency}}.
3
Determine the work done against friction
Wfriction=WinWout=10,000 J8,000 J=2,000 JW_{\text{friction}} = W_{\text{in}} - W_{\text{out}} = 10,000\text{ J} - 8,000\text{ J} = 2,000\text{ J}
The energy wasted as heat and friction is the difference between total work input and useful work output.

Key Concept

Efficiency of Simple Machines and Work Done Against Friction
Question 4Question

A hydraulic press consists of a small effort piston of radius 2 cm2\text{ cm} and a large load piston of radius 8 cm8\text{ cm}. When an effort force of 50 N50\text{ N} is applied to the small piston, it successfully lifts a load of 600 N600\text{ N} placed on the large piston. What is the efficiency of this hydraulic press?

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Answer: 75%75\%

Answer

The efficiency of the hydraulic press is 75%75\%.
The correct answer is 75%75\%. The mechanical advantage is MA=60050=12MA = \frac{600}{50} = 12, and the velocity ratio is VR=(82)2=16VR = \left(\frac{8}{2}\right)^2 = 16. Taking the ratio MAVR×100%\frac{MA}{VR} \times 100\% yields 1216×100%=75%\frac{12}{16} \times 100\% = 75\%.

Step-by-Step Solution

1
Calculate the Mechanical Advantage (MA) of the hydraulic press.
MA=LoadEffort=600 N50 N=12MA = \frac{\text{Load}}{\text{Effort}} = \frac{600\text{ N}}{50\text{ N}} = 12
Mechanical advantage measures the force multiplication factor of a machine.
2
Calculate the Velocity Ratio (VR) of the hydraulic press using the piston radii.
VR=Area of load pistonArea of effort piston=πR2πr2=(8 cm2 cm)2=42=16VR = \frac{\text{Area of load piston}}{\text{Area of effort piston}} = \frac{\pi R^2}{\pi r^2} = \left(\frac{8\text{ cm}}{2\text{ cm}}\right)^2 = 4^2 = 16
For a hydraulic press, velocity ratio equals the ratio of the cross-sectional areas of the pistons, which simplifies to the square of the radii ratio.
3
Compute the efficiency of the machine.
η=MAVR×100%=1216×100%=75%\eta = \frac{MA}{VR} \times 100\% = \frac{12}{16} \times 100\% = 75\%
Efficiency is defined as the ratio of Mechanical Advantage to Velocity Ratio expressed as a percentage.

Key Concept

Mechanical Advantage, Velocity Ratio, and Efficiency of a Hydraulic Press
Estimated Time:1m 30s
Question 5Question

A block and tackle system consisting of 55 pulleys is used to raise a load of 200 N200\text{ N} through a vertical height of 4 m4\text{ m}. If the efficiency of the system is 80%80\%, what is the work done against friction, in joules, during the lifting process?

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Answer: 200

Answer

The work done against friction during the lifting process is 200 J200\text{ J}.
The useful work output is achieved by lifting the 200 N200\text{ N} load through a vertical height of 4 m4\text{ m}, yielding Wout=200×4=800 JW_{\text{out}} = 200 \times 4 = 800\text{ J}. Given an efficiency of 80%80\% (0.800.80), the total work input required from the effort force is Win=8000.80=1000 JW_{\text{in}} = \frac{800}{0.80} = 1000\text{ J}. The energy lost to overcome frictional resistance in the pulleys equals the total work input minus useful work output: 1000 J800 J=200 J1000\text{ J} - 800\text{ J} = 200\text{ J}.

Step-by-Step Solution

1
Calculate useful work output
Wout=800 JW_{\text{out}} = 800\text{ J}
Useful work output is the energy required to raise the load through the specified height (Wout=Load×heightW_{\text{out}} = \text{Load} \times \text{height}).
2
Determine total work input
Win=1000 JW_{\text{in}} = 1000\text{ J}
The total work input is calculated from the efficiency formula: Efficiency=WoutWin\text{Efficiency} = \frac{W_{\text{out}}}{W_{\text{in}}}.
3
Compute work done against friction
Wfriction=200 JW_{\text{friction}} = 200\text{ J}
The work lost overcoming friction is the difference between total work input and useful work output (WinWoutW_{\text{in}} - W_{\text{out}}).

Key Concept

Work and Efficiency in Pulley Systems
Estimated Time:1m 30s
Question 6Question

A machine with a velocity ratio of 66 is used to raise a load of 540 N540\text{ N} by applying an effort of 120 N120\text{ N}. What is the efficiency of the machine?

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Answer: 75%75\%

Answer

The efficiency of the machine is 75%75\%.
The correct option is 75%75\%. Mechanical Advantage is found by dividing the load (540 N540\text{ N}) by the effort (120 N120\text{ N}), giving 4.54.5. Dividing this mechanical advantage by the given velocity ratio (66) and expressing as a percentage yields 4.56×100%=75%\frac{4.5}{6} \times 100\% = 75\%.

Step-by-Step Solution

1
Calculate Mechanical Advantage (MA)
MA=LoadEffort=540 N120 N=4.5\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{540\text{ N}}{120\text{ N}} = 4.5
Mechanical advantage measures the force magnification produced by the machine.
2
CalculateEfficiency(η)Calculate Efficiency (\eta)
η=(MAVR)×100%=(4.56)×100%=75%\eta = \left(\frac{\text{MA}}{\text{VR}}\right) \times 100\% = \left(\frac{4.5}{6}\right) \times 100\% = 75\%
Efficiency is the ratio of Mechanical Advantage to Velocity Ratio multiplied by 100%.

Key Concept

Efficiency of a Simple Machine
Estimated Time:1m 0s
Question 7Question

An inclined plane is set at an angle of 3030^\circ to the horizontal. An effort of 320 N320\text{ N} applied parallel to the plane is used to push a load of 480 N480\text{ N} up the incline at a constant speed. What is the efficiency of the inclined plane expressed as a percentage?

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Answer: 75%; 75; 75 percent

Answer

The efficiency of the inclined plane is 75%75\%.
For an inclined plane inclined at 3030^\circ to the horizontal, the velocity ratio (VR) is given by VR=1sin30=2\text{VR} = \frac{1}{\sin 30^\circ} = 2. The mechanical advantage (MA) is MA=LoadEffort=480 N320 N=1.5\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{480\text{ N}}{320\text{ N}} = 1.5. Dividing MA by VR and multiplying by 100%100\% yields an efficiency of (1.52)×100%=75%\left(\frac{1.5}{2}\right) \times 100\% = 75\%.

Step-by-Step Solution

1
Determine the Velocity Ratio (VR) of the inclined plane from its angle of inclination
VR = \frac{1}{\sin 30^\circ} = \frac{1}{0.5} = 2
For an inclined plane with inclination angle \theta, the velocity ratio is equal to \frac{1}{\sin \theta}.
2
Calculate the Mechanical Advantage (MA)
MA = \frac{\text{Load}}{\text{Effort}} = \frac{480\text{ N}}{320\text{ N}} = 1.5
Mechanical advantage is defined as the ratio of load to effort force.
3
Calculate the efficiency of the machine
\text{Efficiency} = \frac{\text{MA}}{\text{VR}} \times 100\% = \frac{1.5}{2} \times 100\% = 75\%
Efficiency is the ratio of mechanical advantage to velocity ratio expressed as a percentage.

Key Concept

Efficiency of an Inclined Plane
Question 8Question

A screw jack with a pitch of 4 mm4\text{ mm} and a tommy bar of length 56 cm56\text{ cm} is used to raise a heavy load of mass 1100 kg1100\text{ kg}. If an effort force of 50 N50\text{ N} is applied at the outer end of the tommy bar, what is the efficiency of the screw jack? (Take π=227\pi = \frac{22}{7} and g=10 m/s2g = 10\text{ m/s}^2)

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Answer: 25%

Answer

The efficiency of the screw jack is 25%
The mechanical advantage is calculated as MA=11,000 N50 N=220MA = \frac{11,000\text{ N}}{50\text{ N}} = 220. The velocity ratio for a screw jack is VR=2πRp=2×227×0.56 m0.004 m=880VR = \frac{2 \pi R}{p} = \frac{2 \times \frac{22}{7} \times 0.56\text{ m}}{0.004\text{ m}} = 880. Dividing MAMA by VRVR and multiplying by 100%100\% yields an efficiency of 220880×100%=25%\frac{220}{880} \times 100\% = 25\%.

Step-by-Step Solution

1
Calculate the load force (weight) from the given mass.
W=m×g=1100 kg×10 m/s2=11,000 NW = m \times g = 1100\text{ kg} \times 10\text{ m/s}^2 = 11,000\text{ N}
Mass must be converted to weight force in newtons to compute mechanical advantage.
2
Calculate the Mechanical Advantage (MA).
MA=LoadEffort=11,000 N50 N=220MA = \frac{\text{Load}}{\text{Effort}} = \frac{11,000\text{ N}}{50\text{ N}} = 220
Mechanical advantage is the ratio of output load force to input effort force.
3
Calculate the Velocity Ratio (VR) of the screw jack.
VR=2πRp=2×227×0.56 m0.004 m=3.52 m0.004 m=880VR = \frac{2 \pi R}{p} = \frac{2 \times \frac{22}{7} \times 0.56\text{ m}}{0.004\text{ m}} = \frac{3.52\text{ m}}{0.004\text{ m}} = 880
Velocity ratio is the distance moved by the effort in one full revolution (2πR2\pi R) divided by the distance moved by the load in one revolution (pitch pp).
4
Calculate the efficiency of the machine.
Efficiency=MAVR×100%=220880×100%=25%\text{Efficiency} = \frac{MA}{VR} \times 100\% = \frac{220}{880} \times 100\% = 25\%
Efficiency is defined as the ratio of Mechanical Advantage to Velocity Ratio multiplied by 100%.

Key Concept

Mechanical Advantage, Velocity Ratio, and Efficiency of a Screw Jack
Question 9Question

A wheel and axle system consists of a wheel with a radius of 25 cm25\text{ cm} attached to an axle with a radius of 5 cm5\text{ cm}. What is the velocity ratio of this machine?

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Answer: 5

Answer

The velocity ratio of the machine is 5.
The velocity ratio (VR) of a wheel and axle is the ratio of the radius of the wheel (RR) to the radius of the axle (rr). Calculating 25 cm5 cm\frac{25\text{ cm}}{5\text{ cm}} gives a velocity ratio of 55.

Step-by-Step Solution

1
Identify the formula for the velocity ratio of a wheel and axle system.
VR=Rr\text{VR} = \frac{R}{r}
Velocity ratio is defined as the distance moved by the effort (proportional to wheel radius) divided by the distance moved by the load (proportional to axle radius).
2
Substitute the given values into the formula.
VR=25 cm5 cm\text{VR} = \frac{25\text{ cm}}{5\text{ cm}}
The radius of the wheel R=25 cmR = 25\text{ cm} and the radius of the axle r=5 cmr = 5\text{ cm}.
3
Calculate the final ratio.
VR=5\text{VR} = 5
Dividing 25 by 5 yields 5. The ratio is dimensionless because the units of centimeters cancel out.

Key Concept

Velocity Ratio of a Wheel and Axle
Question 10Question

A wheel and axle machine has a wheel of radius 25 cm25\text{ cm} and an axle of radius 5 cm5\text{ cm}. If an effort force of 100 N100\text{ N} is applied to lift a load of 400 N400\text{ N}, what is the efficiency of the machine?

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Answer: 80%80\%

Answer

The efficiency of the wheel and axle machine is 80%80\%.
First, calculate the velocity ratio as the ratio of wheel radius to axle radius: VR=255=5\text{VR} = \frac{25}{5} = 5. Next, calculate mechanical advantage as load over effort: MA=400100=4\text{MA} = \frac{400}{100} = 4. Finally, calculate efficiency by dividing mechanical advantage by velocity ratio: Efficiency=45×100%=80%\text{Efficiency} = \frac{4}{5} \times 100\% = 80\%.

Step-by-Step Solution

1
Calculate the Velocity Ratio (VR) of the wheel and axle system
VR=Radius of WheelRadius of Axle=25 cm5 cm=5\text{VR} = \frac{\text{Radius of Wheel}}{\text{Radius of Axle}} = \frac{25\text{ cm}}{5\text{ cm}} = 5
For a wheel and axle, the velocity ratio is the ratio of the radius of the wheel to the radius of the axle.
2
Calculate the Mechanical Advantage (MA) of the machine
MA=LoadEffort=400 N100 N=4\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{400\text{ N}}{100\text{ N}} = 4
Mechanical advantage measures the force magnification of a machine, defined as the ratio of load raised to effort applied.
3
Calculate the Efficiency of the machine
Efficiency=MAVR×100%=45×100%=80%\text{Efficiency} = \frac{\text{MA}}{\text{VR}} \times 100\% = \frac{4}{5} \times 100\% = 80\%
Efficiency is defined as the ratio of Mechanical Advantage to Velocity Ratio expressed as a percentage.

Key Concept

Efficiency of Simple Machines
Question 11Question

A hydraulic press has a small piston with a diameter of 4 cm4\text{ cm} and a large piston with a diameter of 20 cm20\text{ cm}. If an effort force of 80 N80\text{ N} applied to the small piston raises a load of 1500 N1500\text{ N} placed on the large piston, what is the efficiency of the machine?

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Answer: 75.0%75.0\%

Answer

The efficiency of the hydraulic press is 75.0%75.0\%.
The mechanical advantage is MA=150080=18.75MA = \frac{1500}{80} = 18.75. The velocity ratio for pistons of diameters 20 cm20\text{ cm} and 4 cm4\text{ cm} is VR=(204)2=25VR = \left(\frac{20}{4}\right)^2 = 25. Efficiency is MAVR×100%=18.7525×100%=75.0%\frac{MA}{VR} \times 100\% = \frac{18.75}{25} \times 100\% = 75.0\%.

Step-by-Step Solution

1
Calculate Mechanical Advantage (MA)
MA=LoadEffort=1500 N80 N=18.75MA = \frac{\text{Load}}{\text{Effort}} = \frac{1500\text{ N}}{80\text{ N}} = 18.75
Mechanical advantage is defined as the ratio of load force to effort force.
2
Calculate Velocity Ratio (VR) for the hydraulic press
VR=A2A1=(d2d1)2=(20 cm4 cm)2=52=25VR = \frac{A_2}{A_1} = \left(\frac{d_2}{d_1}\right)^2 = \left(\frac{20\text{ cm}}{4\text{ cm}}\right)^2 = 5^2 = 25
The velocity ratio of a hydraulic press equals the ratio of the cross-sectional areas of the pistons, which simplifies to the square of the ratio of their diameters.
3
CalculateEfficiency(η)Calculate Efficiency (\eta)
\eta = \frac{MA}{VR} \times 100\% = \frac{18.75}{25} \times 100\% = 75.0\%
Efficiency is the ratio of mechanical advantage to velocity ratio expressed as a percentage.

Key Concept

Hydraulic Press Efficiency and Velocity Ratio
Question 12Question

A simple machine lifts a load of 200 N200\text{ N} when an effort of 50 N50\text{ N} is applied to it. What is the mechanical advantage of the machine?

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Answer: 4; 4.0

Answer

The mechanical advantage of the machine is 44.
Mechanical Advantage (MA) is the ratio of the force exerted by the machine (load) to the force applied to the machine (effort). Dividing 200 N200\text{ N} by 50 N50\text{ N} yields a dimensionless mechanical advantage of 44.

Step-by-Step Solution

1
Identify the given values from the problem statement
Load (LL) = 200 N200\text{ N}, Effort (EE) = 50 N50\text{ N}
Mechanical advantage is defined as the ratio of load to effort.
2
Apply the formula for Mechanical Advantage (MA)
\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{200\text{ N}}{50\text{ N}} = 4
Dividing the output force by the input force gives the force amplification factor of the machine.

Key Concept

Mechanical Advantage of Simple Machines
Estimated Time:45s
Question 13Question

A simple machine with a velocity ratio of 55 requires an effort of 200 N200\text{ N} to raise a load of 800 N800\text{ N}. What is the efficiency of the machine in percentage?

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Answer: 80%; 80; 80 percent; 80 %

Answer

The efficiency of the machine is 80%80\%.
The mechanical advantage is calculated by dividing the load (800 N800\text{ N}) by the effort (200 N200\text{ N}), yielding MA=4\text{MA} = 4. Dividing the mechanical advantage by the velocity ratio (55) and multiplying by 100%100\% gives an efficiency of 80%80\%.

Step-by-Step Solution

1
Calculate the Mechanical Advantage (MA) of the machine
MA=LoadEffort=800 N200 N=4\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{800\text{ N}}{200\text{ N}} = 4
Mechanical Advantage is defined as the ratio of the force overcome (load) to the force applied (effort).
2
Calculate the Efficiency using Mechanical Advantage and Velocity Ratio
Efficiency=(MAVR)×100%=(45)×100%=80%\text{Efficiency} = \left(\frac{\text{MA}}{\text{VR}}\right) \times 100\% = \left(\frac{4}{5}\right) \times 100\% = 80\%
Efficiency is the ratio of Mechanical Advantage to Velocity Ratio expressed as a percentage.

Key Concept

Efficiency of a Simple Machine
Estimated Time:1m 30s
Question 14Question

A gear system consists of a driving gear with 1212 teeth and a driven gear with 4848 teeth. If an effort of 40 N40\text{ N} applied to the driving gear overcomes a load of 120 N120\text{ N} on the driven gear, what is the efficiency of the machine?

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Answer: 75%; 75 %; 75 percent; 75

Answer

The efficiency of the gear system is 75%.
The velocity ratio is determined by dividing the number of teeth on the driven gear (48) by the number of teeth on the driving gear (12), giving a VR of 4. The mechanical advantage is the ratio of load (120 N) to effort (40 N), giving an MA of 3. Dividing the mechanical advantage by the velocity ratio and multiplying by 100 yields an efficiency of 75%.

Step-by-Step Solution

1
Calculate the velocity ratio (VR) of the gear system.
VR = 4
For a gear system, the velocity ratio is the ratio of the number of teeth on the driven gear to the number of teeth on the driving gear: VR=NdrivenNdriving=4812=4\text{VR} = \frac{N_{\text{driven}}}{N_{\text{driving}}} = \frac{48}{12} = 4.
2
Calculate the mechanical advantage (MA) of the gear system.
MA = 3
Mechanical advantage is the ratio of the load to the effort: MA=LoadEffort=120 N40 N=3\text{MA} = \frac{\text{Load}}{\text{Effort}} = \frac{120\text{ N}}{40\text{ N}} = 3.
3
Calculate the efficiency of the gear system.
Efficiency = 75%
Efficiency is given by the formula: Efficiency=MAVR×100%=34×100%=75%\text{Efficiency} = \frac{\text{MA}}{\text{VR}} \times 100\% = \frac{3}{4} \times 100\% = 75\%.

Key Concept

Efficiency, Mechanical Advantage, and Velocity Ratio of a Gear System
Estimated Time:1m 30s
Question 15Question

An inclined plane of length 10 m10\text{ m} is used to raise a heavy crate of load 900 N900\text{ N} to a height of 2 m2\text{ m}. If an effort force of 250 N250\text{ N} is applied parallel to the inclined surface to push the crate up at constant speed, what is the efficiency of the simple machine?

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Answer: $72\%

Answer

The efficiency of the inclined plane is 72%72\%.
The mechanical advantage of the machine is MA=900 N250 N=3.6MA = \frac{900\text{ N}}{250\text{ N}} = 3.6, and its velocity ratio is VR=10 m2 m=5VR = \frac{10\text{ m}}{2\text{ m}} = 5. Dividing MAMA by VRVR and multiplying by 100%100\% gives an efficiency of 72%72\%.

Step-by-Step Solution

1
Calculate the Mechanical Advantage (MA)
MA=LoadEffort=900 N250 N=3.6MA = \frac{\text{Load}}{\text{Effort}} = \frac{900\text{ N}}{250\text{ N}} = 3.6
Mechanical advantage is defined as the ratio of load force to effort force.
2
Calculate the Velocity Ratio (VR) of the inclined plane
VR=Length of planeHeight of plane=10 m2 m=5VR = \frac{\text{Length of plane}}{\text{Height of plane}} = \frac{10\text{ m}}{2\text{ m}} = 5
Velocity ratio for an inclined plane is the ratio of distance moved by effort along the incline to distance moved by load vertically.
3
CalculatetheEfficiency(η)Calculate the Efficiency (\eta)
\eta = \left(\frac{MA}{VR}\right) \times 100\% = \left(\frac{3.6}{5}\right) \times 100\% = 72\%
Efficiency is the ratio of Mechanical Advantage to Velocity Ratio, expressed as a percentage.

Key Concept

Efficiency of an Inclined Plane
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