Question

Gravitational potential energy (U) depends on three things: the object’s mass (m), its height (h), and gravitational acceleration (g), which is 9.81 m/s2 on Earth’s surface: U = mgh Energy is measured in joules (J). One joule is equal to one 1 kg•m2/s2. When calculating the energy of an object, it is helpful to convert the mass and height to kilograms and meters.
A. What is the mass of the 50-gram car, in kilograms?

B. Set Hill 1 to 75 cm and the other hills to 0 cm. What is the height in meters?

C. What is the potential energy of the car, in joules?

Answer 1

A. 500N

B. 0.75 m

C. 7865432J

Answer 2

Explanation:

A. Mass of the car ,m = 50 g

1 g = 0.001 kg

50 g = 0.001 × 50 kg = 0.05 kg

B. Height of hill ,h= 75 cm = 0.75 m

1 cm = 0.01 m

Height of other hill ,h' = 0 cm = 0 m

C. Gravitational potential energy (U):

$U=mgh$

Mass of car = m = 0.05 kg

Height at which car is = h = 0.75 m

$U= 0.05 kg\times 0.75 m\times 9.8 m/s^2=0.3675 kg/m^2/s^2=0.3675 J$