The Gravitational PE (U) depends on three things: the object’s mass (m), its height (h), and gravitational acceleration (g), which is 9.81 m/s^2 on Earth’s surface.
so U = mgh = 9.81mh on earth
mass of the car = 50.0 grams = 0.05kg
height, h:
Hill 1 = 90.0 cm = 0.9m,
Hill 2 = 65.0 cm = 0.65m,
Hill 3 = 20.0 cm = 0.2m
substitute into eqn U = mgh
U @ top of Hill 1 = 0.05*9.81*0.9 = 0.4415J
U @ top of Hill 2 = 0.05*9.81*0.65 = 0.3188J
U @ top of Hill 3 = 0.05*9.81*0.2 = 0.0981J
difference in Gravitational Potential Energy from the top of Hill 1 to the top of Hill 3 = 0.4415 - 0.0981
= 0.3434J where J is the unit for energy, Joules
Given:
u=0 m/s
a=1.1 m/s^2
S=5 m
t=time it takes to run 5 m
Use the kinematics equation
S=ut+(1/2)at^2
=>
5=0*t+(1/2)1.1(t^2)
solve for t
t=sqrt(5*2/1.1)=3.015 seconds.
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