Question

A 7.0 kg toy car can move along an x axis. The figure gives Fx of the force acting on the car, which begins at rest at time t = 0. The scale on the Fx axis is set by Fxs = 4.0 N. IN UNIT VECTOR NOTATION PLEASE, what is P at (a)t = 2.0 s and (b)t = 7.0 s,(c) what is v at t = 2.0 s? PLEASE PUT ANSWER IN UNIT VECTOR NOTATION

F (N) -F3S

Answer 1

mass of car $m=7.0\,kg$

(a) Initial velocity = 0 m/s, Initial momentum = 0.

change in momentum is area below the F-t curve

Hence momentum at t = 2.0 s is $\frac{1}{2}\times\,2\times\,8=8\hat{i}\,kg.m/s$

(b) momentum at t = 7.0 s is $\frac{1}{2}\times\,2\times\,8+2\times\,8+\frac{1}{2}\times\,2\times\,8-\frac{1}{2}\times\,1\times\,4=30\hat{i}\,kg.m/s$

(c) speed at time t = 2.0 s is 8/7 = 1.14 $\hat{i}\,m/s$