Chapter 8, Problem 55A

A 1000-kg car moving at 20 m/s slams into a building and comes to a halt. Which of the following questions can be answered using the given information, and which one cannot be answered? Explain.

a. What impulse acts on the car?

b. What is the force of impact on the car?

To determine

To Calculate: The impulse that acts on the car.

Answer to Problem 55A

  $-20000\text{N}\cdot \text{s}$

Explanation of Solution

Given:

The velocity of the car is $u=20\text{m/s}$ .

And, the weight of the car is $m=1000\text{ kg}$ .

Formula used:

The change in momentum to:

  $\Delta p=m\left(v-u\right)$

Here, m is the mass, v is the final velocity and u is the initial velocity.

Impulse = $\Delta p$

Calculation:

  $\begin{array}{r}\Delta p=m\left(v-u\right)\\ =1000\left(0-20\right)\\ =-20000\text{N}\cdot \text{s}\end{array}$

Conclusion:

The impulse act on the car is $-20000\text{N}\cdot \text{s}$ .

To determine

To Calculate: The force of impact on the car.

Answer to Problem 55A

It is not possible to solve.

Explanation of Solution

It is not possible to calculate the force of impact on the car because in order to solve for the force, there must be information about the amount of time elapsed for the change in momentum.

Conclusion:

Thus,this calculation is not possible.