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Question

Difficulty: EasyWork, Energy and Power

A toy car of mass 0.5 kg0.5\text{ kg} moves along a smooth horizontal surface at a constant speed of 4 m s−14\text{ m s}^{-1}. What is the kinetic energy of the toy car?

  1. A
    1 J1\text{ J}
  2. 4 J4\text{ J}Answer
  3. C
    8 J8\text{ J}
  4. D
    16 J16\text{ J}

Answer

The kinetic energy of the toy car is 4 J4\text{ J}.
Substituting the given values into the formula Ek=12mv2E_k = \frac{1}{2} m v^2 gives Ek=12×0.5×42=4 JE_k = \frac{1}{2} \times 0.5 \times 4^2 = 4\text{ J}.

Step-by-Step Solution

1
Identify the given physical quantities
Mass m=0.5 kgm = 0.5\text{ kg} and speed v=4 m s−1v = 4\text{ m s}^{-1}.
These are the mandatory inputs needed to determine kinetic energy.
2
Apply the kinetic energy formula
Ek=12mv2E_k = \frac{1}{2} m v^2
Kinetic energy of a translational body is defined as half the product of its mass and the square of its speed.
3
Substitute the values and compute the result
Ek=12×0.5 kg×(4 m s−1)2=0.25×16=4 JE_k = \frac{1}{2} \times 0.5\text{ kg} \times (4\text{ m s}^{-1})^2 = 0.25 \times 16 = 4\text{ J}.
Evaluating the mathematical operation yields the energy in Joules.

Key Concept

Kinetic Energy
Estimated Time:45s
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Topics

Work, Energy and Power

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