Question

Difficulty: HardWork, Energy, and Power

Four mobile systems are evaluated during performance trials on a flat testing course. Arrange the systems in order of their kinetic energy, from least to greatest.

  1. 1A 500 kg500\text{ kg} cargo transport moving at 4 m/s4\text{ m/s}
  2. 2A 10 kg10\text{ kg} automated inspection rover moving at 30 m/s30\text{ m/s}
  3. 3A 40 kg40\text{ kg} tracked reconnaissance unit moving at 20 m/s20\text{ m/s}
  4. 4A 2 kg2\text{ kg} calibration projectile moving at 100 m/s100\text{ m/s}

Answer

From least to greatest kinetic energy: the 500 kg500\text{ kg} cargo transport (4000 J4{}000\text{ J}), the 10 kg10\text{ kg} automated inspection rover (4500 J4{}500\text{ J}), the 40 kg40\text{ kg} tracked reconnaissance unit (8000 J8{}000\text{ J}), and the 2 kg2\text{ kg} calibration projectile (10000 J10{}000\text{ J}).
Applying the kinetic energy formula KE=12mv2KE = \frac{1}{2}mv^2 to each system yields 4000 J4{}000\text{ J} for the 500 kg500\text{ kg} transport at 4 m/s4\text{ m/s}, 4500 J4{}500\text{ J} for the 10 kg10\text{ kg} rover at 30 m/s30\text{ m/s}, 8000 J8{}000\text{ J} for the 40 kg40\text{ kg} unit at 20 m/s20\text{ m/s}, and 10000 J10{}000\text{ J} for the 2 kg2\text{ kg} projectile at 100 m/s100\text{ m/s}. Arranging these values from smallest to largest produces the correct sequence.

Step-by-Step Solution

1
Identify the formula for kinetic energy.
KE=12mv2KE = \frac{1}{2}mv^2, where mm is mass in kilograms and vv is velocity in meters per second.
Kinetic energy is directly proportional to mass and proportional to the square of velocity.
2
Calculate the kinetic energy for each of the four systems.
Cargo transport: 12(500)(42)=250×16=4000 J\frac{1}{2}(500)(4^2) = 250 \times 16 = 4{}000\text{ J}; Inspection rover: 12(10)(302)=5×900=4500 J\frac{1}{2}(10)(30^2) = 5 \times 900 = 4{}500\text{ J}; Reconnaissance unit: 12(40)(202)=20×400=8000 J\frac{1}{2}(40)(20^2) = 20 \times 400 = 8{}000\text{ J}; Calibration projectile: 12(2)(1002)=1×10000=10000 J\frac{1}{2}(2)(100^2) = 1 \times 10{}000 = 10{}000\text{ J}.
Quantitative values allow direct comparison across all systems.
3
Arrange the resulting energy values in ascending sequence.
4000 J<4500 J<8000 J<10000 J4{}000\text{ J} < 4{}500\text{ J} < 8{}000\text{ J} < 10{}000\text{ J}.
Orders the systems from least kinetic energy to greatest kinetic energy as required.

Key Concept

Kinetic energy is calculated as KE=12mv2KE = \frac{1}{2}mv^2, meaning velocity has a quadratic effect compared to the linear effect of mass.
Estimated Time:1m 30s
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