A force of 20 N acts on a body of mass 4 kg for 5 s when it is initially at rest. Calculate the velocity acquired by the body and change in momentum of the body. [3 MARKS]
Solution: 1 Mark per step
Step 1:
Given, force, F=20 N, mass, m=4 kg, initial velocity u=0 and time, t=5 s.
Let acceleration be a.
According to Newton's second law, F=ma.
So, a=Fm=204=5 m s−2
Step 2:
Let the final velocity acquired by the body be v.
∵v=u+at
v=0+5×5=25 m s−1
Step 3:
Momentum =mv=25×4=100 kg m s−1