Chapter 9, Problem 54A

To determine

The speed with which a hockey puck head towards the goal.

Answer to Problem 54A

  $41.74\text{m/s}$

Explanation of Solution

Given:

The mass of the puck, $m=\text{ 0}\text{.115}\text{kg}$

Since initially the puck was at rest, thus initial velocity of the puck is $v_i=0\text{m/s}$

Force exerted on the puck, $F=30.0\text{N}$

Time taken, $\Delta t=\text{ 0}\text{.16 s}$

Formula used:

Momentum of an object of mass m and moving with velocity v is given by,

  $p=mv$

Impulse on an object is equal to the change in momentum of an object,

  $\text{Impulse = }F\Delta t=p_f-p_i$

where $F$ is the applied force for time $\Delta t$ , $p_f$ is the final momentum, $p_i$ is the initial momentum.

Calculation:

Let the speed with which the puck head towards the goal, that is the final velocity of the puck be $v_f$ .

Using all the given values in the formula mentioned above, the final velocity on the puck will be,

  $\begin{array}{c}F\Delta t=m\left(v_f-v_i\right)\\ 30\left(0.16\right)=0.115\left(v_f-0\right)\\ v_f=41.74\text{m/s}\end{array}$

Conclusion:

Thus, the speed with which the puck head towards the goal is $41.74\text{m/s}$ .