Q4.5 Work and kinetic energy I (S)
A 30 g bullet, initially travelling at 500 ms-1, penetrates 12 cm into a solid wall.- Calculate the average work done by the wall in stopping the bullet.
- Assuming that the wall exerts a constant force on the bullet, calculate the magnitude of that force.
Solution
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Solution
The work done by the wall is simply the change in kinetic energy of the bullet. The change in kinetic energy is negative; therefore so is the work done by the wall:
-0.5×0.03×500×500=-3750 JIf the force provided by the wall is constant, then the total work done by the wall in distance d is
W=FdWith d=12 cm, the magnitude of the average force is 3750/0.12 = 31250 N