Question

A force exerted an impulse on a particle changing its speed from u to 2u the applied force and the intiallattached velocity are opposite directed along the same line the work done by the force

Answer 1

1. impulse j = f.dt = change in momentum =mv-mu.....1
2. w = f.d
3. and v2-u2= 2ad
4. therefore d = v2-u2/2a
5. put d in w = f.d
6. w = f.(v2-u2)/2a
7. w = f.(v+u)(v-u)/2a
8. now since f=ma,a/f=m
9. therefore w =m(v-u)(v+u)/2
10. now mv-mu = change in momentum =j
11. therefore w = j(v+u)/2
12. Here v=2u
13. Therefore w=3ju/2