Question

A 1,000 kg car is moving at 20 m/s, and slams into a building before coming to a halt.

Answer 1

Hi there!

We can calculate linear momentum using the following:
$\large\boxed{p = m v}$

p = linear momentum (kgm/s)
m = mass (kg)
v = velocity (m/s)

Calculate:

$p = 1000 * 20 = 20000 kg\frac{m}{s}$

Now, we can relate force, time, and momentum with the following:
$\large\boxed{I = Ft}$

I = Impulse (kgm/s)
F = Force (N)
t = time (s)

Rearrange to solve for force:
$F = \frac{I}{t}$

The impulse is equal to the change in momentum. Since the car comes to a halt, all of its momentum is lost, so:

$I = \Delta p = p_f - p_i = 0 - 20000 = -20000$

Solve:
$F = \frac{-20000}{0.5} = \boxed{-40000N}$

**Negative force since the positive direction is towards the wall, and the negative direction is away from the wall.