Question

The brakes are applied on a car traveling at 30. m/s [fwd]. The car stops in 3.0s. What is its displacement during this time?

The answer is 45 m [fwd], but I do not understand how to get to this answer.

Answer 1

You can use the equations of motion to find the displacement, as shown below.

Explanation:

If we are assuming that the acceleration is uniform (which I believe must be the case), you can use the following equation of motion, as it does not require that you know, or first calculate the acceleration:

`Deltad=1/2 (v_i+v_f) Deltat`

This basically says that the displacement `Deltad` is equal to the average speed `1/2 (v_i+v_f)` multiplied by the time interval `Deltat`.

Insert the numbers

`Deltad=1/2 (30+0) (3) = 15(3)=45m`