Answer:
0.74 m/s
Explanation:
From the question,
We apply the law of conservation of momentum,
Total momentum before collision = Total momentum after collision.
Since the skateboard, the person and the brick where stationary, therefore, the total momentum before collision is 0
0 = Total momentum after collision
(m+M)V + m'v = 0
Where m = mass of the skateboard, M = mass of the person, m' = mass of the brick, V = recoil velocity of the person and the skateboard, v = velocity of the brick
make V the subject of the equation above
V = -m'v/(m+M)................... Equation 1
Given: m = 4.10 kg, M = 68.0 kg, m' = 2.50 kg, v = 21.0 m/s.
Substitute these values into equation 1
V = -(2.5×21)/(68+2.5)
V = 52.50/70.5
V = 0.74 m/s
