Question

A 90 kg man lying on a frictionless surface throw a
68 g stone away from him, giving it a speed of 4.0
m/s. What velocity does the man acquire as a result?​

Answer 1

Explanation:

No external forces with horizontal components act on the man-stone system and the sum of the vertical forces to zero, so the total momentum of the system is conserved. Since the man and the stone are initially at rest, the total momentum is zero both before and after the stone is kicked. Let m

s

be the mass of the stone and ν

s

be its velocity after it is kicked; let m

m

be the mass of the man and ν

m

be his velocity after he kicks the stone. Then

m

s

ν

s

+m

m

ν

m

=0→ν

m

=−m

s

ν

s

/m

m

.

We take the axis to be positive in the direction of the motion of the stone. Then

ν

m

=−

91kg

(0.068kg)(4.0m/s)

=−3.0×10

−3

m/s.

or ∣ν

m

∣=3.0×10

−3

m/s . The negative sign indicates that the man moves in the direction opposite to the direction of motion of the stone .

Answer verified by Toppr