# Find velocity using Force -time graph

1. Feb 24, 2015

### jake jungle

1. The problem statement, all variables and given/known data

The variation of the force F with the time t acting on a body of mass 200g is as shown in the graph below
Given that the velocity of the body at t=75ms is 15m/s . What is the velocity of the body at t=150ms
A.15m/s
B.30m/s
C.35m/s
D.39m/s
2. Relevant equations
F = m Δv/Δt

3. The attempt at a solution
so i calculate the area of ABCDE , and it equal the change of momentum from 75ms to 150ms
the i calculate the momentum of the body in t = 75ms using v = 15m/s and mass of 200g
=> momentum of the body in t = 150ms => v
however i dont get any answer in the choices . please tell me where i was wrong

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2. Feb 24, 2015

### Orodruin

Staff Emeritus
It will be easier to know where you go wrong if you provide your actual computations rather than describing them in words. The general idea is correct.

3. Feb 24, 2015

### Quantum Defect

v = v_0 + integral [dt*F/m]

Units matter. The area of the first bit (75 ms - 100 ms): [ 70 N * 25 x 10^-3 sec / 200 x 10^-3 kg -- factors of 10^-3 cancel = 8.75 m/s]