A swimmer dives horizontally off a 500 kg raft. If the diver’s mass is 75 kg and his speed while leaving the raft is 4 m/s, what is the raft speed?
A. 0.2 m/s
B. 0.5 m/s
C. 0.6 m/s
D. 4.0 m/s
E. none of these
Impulse is:
A. the same as momentum.
B. force times distance.
C. distance times time.
D. force times the time which the force acts.
E. none of the above
If no forces are acting on a moving object, the object will continue to move with constant:
A. impulse
B. momentum
C. acceleration
D. all of these
E. none of these
1 Answer

1) Linear momentum is simply equal to mass (m) times velocity (v). Since the diver and the raft are pushing off of each other, their linear momentum will be the same.
m1*v1 = m2*v2
This is what we know: m1 = 75 kg, v1 = 4 m/s, and m2 = 500 kg.
Hence, 75 kg * 4 m/s = 500 kg * v2…. v2=0.6
2) impulse is defined as “the integral of force with respect to time.” I would say C.
3)
(A) doesn’t work because impulse is a function of a force, and there are no forces involved.
(B) is a function of velocity and mass. Newton’s 1st and 2nd laws dictate that velocity will remain constant if there are no forces involved.
(C) doesn’t work because acceleration requires a force.
(D) nope.
(E) from the above answers, I would say (B) is the right answer.