Kevin S. Huang

2013: Problems 8-9

Topic: Energy
Concepts: Work-energy theorem

Solution:

By the work-energy theorem,

W=\Delta K=K_f-K_i

We have

-Fx=0-K_i

K_i=Fx

so the answer is A.

Topic: Energy
Concepts: Kinetic energy

Solution:

From the previous problem, we found the initial kinetic energy is

K_i=\frac{1}{2}mv^2=Fx

Solving for the mass,

m=\frac{2Fx}{v^2}

Then the initial momentum is

p_i=mv=\frac{2Fx}{v}

so the answer is E.