Question

Determine the gravitational potential energy of the 500 g cart with respect to the floor if it were to sit at rest on a table in your home. Direction 1 KE = 0.076 kg *m/s Direction 2 KE = 0.190 kg*m/s.

1. What specific data do you need to collect to determine the potential energy of the cart?

2. Record these data, clearly identifying each numerical value and its units.

3. Calculate the potential energy of the cart.

4. Why was it necessary to state "with respect to the floor"?

5. If you lift the cart from the floor to the table top at constant speed, find the work you do on the cart.

6. Why are the work and the potential energy you found in (c) the same?

Answer 1

Gravitational potential energy (GPE) depends on the height from the reference level. So we need to find the height of the table.

                 GPE = mgh

So you have mass m=500g = 0.5 kg

acceleration due to gravity g = 9.8 m/s^2

But collecting data for height of table and putting the values in above equation we get the gravitational potential energy.

Gravitational potential energy is always calculated with respect to some reference level where we assume GPE = 0. And we calculate the change in GPE at two points. Also w usually consider earth surface as the reference level.

As per the energy conservation, work done is equal to the change in potential energy in case if there is no dissipative work done such as friction.