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Homework Statement
An object of mass m moving in a certain direction has a kinetic energy of 4.0 J.It hits a wall and comes back with half its original kinetic energy.
Homework Equations
If the speed of the object on return is 2.0 m/s, what is the mass of the object?
A) 2.8 kg
B) 3.8 kg
C) 1.0 kg
D) 4.0 kg
The Attempt at a Solution
let mass of object = m
speed on return =2
kinetic energ on return = 0.5 m *v*v
kinetic energy initial =0.5*m*v1*v1
kf=0.5 ki
therefor v1= (2)^0.5 v
v1 =2.828 m/s
initial kinetic energy = 4 j
4=0.5*m*v1^2
8=m* 8
m=1 kg
My problem:
I don't understand the solution, nor what formula to use. Please help. Thanks.
I need to know why Answer: C is correct.