Consider the conservation of energy equation below. A ball of mass m falls from
ID: 1424305 • Letter: C
Question
Consider the conservation of energy equation below. A ball of mass m falls from a height h to the floor. Identify the appropriate version of the equation above for the system of the ball and the Earth Use this equation to calculate the speed of the ball just before It strikes the Earth. (Use the following as necessary: m for mass, ft for height, g for acceleration due to gravity.) Identify the appropriate version of the equation above for the system of the ball. Use this equation to calculate the speed of the ball just before it strikes the Earth. (Use the following as necessary: m tor mats, m for height, g for acceleration due to gravity.)Explanation / Answer
a) KE + PE = constant for ball and earth system
Ki + Ui = Kf + Uf
Kf-Ki + Uf-Ui = 0
deltaK + deltaU = 0
(0 - mv^2 /2 ) + ( mgh - 0) = 0
v = sqrt(2gh)
b) initially ball had PE and KE zero but as it comes down to earth level PE =0 and KE had some value.
using work energy theorem on ball.
work done by gravity = changein KE
w = deltak
so mgh = (mv^2 /2) - ( 0 )
v = sqrt(2gh)