Question

3.2.2 quiz: momentum
question 8 of 10
two hockey players are about to collide on the ice. one player has a mass of 70 kg and is traveling at 1.4 m/s north. the other has a mass of 75 kg and is traveling at 1.0 m/s south. the system consists of the two hockey players.
according to the law of conservation of momentum, what is the total momentum of the system after they collide? assume the collision is an elastic collision.
a. 23 kg·m/s north
b. 23 kg·m/s south
c. 173 kg·m/s north
d. 173 kg·m/s south

Explanation:

Step1: Define the momentum formula

Momentum $p = mv$, where $m$ is mass and $v$ is velocity. Let north - direction be positive and south - direction be negative.

Step2: Calculate the momentum of the first player

For the first player with $m_1=70$ kg and $v_1 = 1.4$ m/s, $p_1=m_1v_1=70\times1.4 = 98$ kg·m/s.

Step3: Calculate the momentum of the second player

For the second player with $m_2 = 75$ kg and $v_2=- 1.0$ m/s, $p_2=m_2v_2=75\times(-1.0)=-75$ kg·m/s.

Step4: Calculate the total initial momentum

The total initial momentum $p_{total}=p_1 + p_2=98+( - 75)=23$ kg·m/s.
According to the law of conservation of momentum, the total momentum before the collision is equal to the total momentum after the collision in an elastic collision. Since $p_{total}=23$ kg·m/s and the positive value indicates the north - direction.

Answer:

A. 23 kg·m/s north