Question

A 21.0 kg shopping cart is moving with a velocity of 4.0 m/s. It strikes a 9.0 kg box that is initially at rest. They stick together and continue moving at a new velocity. Assume that friction is negligible. What was the momentum of the shopping cart before the collision? 0 kg⋅m/s 36 kg⋅m/s 168 kg⋅m/s 84.0 kg⋅m/s What was the momentum of the box before the collision? 168 kg⋅m/s 84.0 kg⋅m/s 0 kg⋅m/s 36 kg⋅m/s What is the velocity of the combined shopping cart–box wreckage after the collision? 9.3 m/s 4.0 m/s 2.8 m/s 0 m/s

Answer 1

Answer:

a) 84 kg.m/s

b) 0 kg.m/s

c) 2.8 m/s

Explanation:

The momentum of the cart before the collision is given by:

$p_c=m_c*v_c\\p_c=21.0kg*4.0m/s\\p_c=84kg.m/s$

The momentum of the box before the collision is given by:

$p_b=m_b*v_b\\p_c=9.0kg*0m/s\\p_c=0kg.m/s$

Using the linear momentum conservation formula:

$p_c+p_b=(m_c+m_b)*v\\\\v=\frac{84kg.m/s}{30.0kg}\\v=2.8m/s$