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Question

Two go-karts are pushed from the same starting point with the same constant force. They are each pushed a distance of 5 meters. One go-kart is two times as heavy as the lighter one. Which go-kart has less kinetic energy after the 5 meters?

A) the lighter go-kart

B) the heavier go-kart

C) they have the same

D) there is no way to tell

Answer 1

Hello,

There are two different concepts you need to solve this problem: Work and Conservation of Energy.

We know that the equation for work is W = F*d, or the work is equal to the force time the distance.

Since the carts are pushed the same distance with the same force, the work done to the carts is the same.

Work is also a form of energy, and conservation of energy implies that the work done to the carts is converted into another form of energy.

Some common types of energy you may have discussed in your class are kinetic energy, gravitational potential energy, and thermal (or heat) energy.

Gravitational potential energy expresses how it costs energy to do something like go up a hill. Since we aren't told about any hills or inclines, we can assume that there is no change in gravitational potential energy.

Thermal energy is usually dissipated by a frictional force in mechanics problem, but in this problem we aren't told about any friction forces, so we should be good to assume that the change in thermal energy is also zero.

This implies that all of the energy from the work is converted into kinetic energy.

Therefore since the work done to the carts is the same, the kinetic energy is also the same.

This implies that the answer is C) they have the same.

Hopefully this explanation was helpful.