Two passenger cars, X and Y

PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

Two passenger cars, X and Y, travel along a straight, level track. • Car X has mass

1.2\times10^{3}\,\text{kg}

and moves at

22\,\text{m}\!\cdot\!\text{s}^{-1}

. • Car Y has mass

1.8\times10^{3}\,\text{kg}

. (a) Determine the speed that car Y must have so that its translational kinetic energy equals that of car X. Show your work and express the answer with appropriate units. (b) Suppose instead that car Y travels at

25\,\text{m}\!\cdot\!\text{s}^{-1}

. Calculate the factor by which its kinetic energy exceeds that of car X and state whether this factor is greater than or less than 1.

Related theory

Kinetic Energy
Kinetic energy and the work-energy theorem
Work, Energy and Power
Linear momentum

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