Question

Estimate the acceleration you subject yourself to if you walk into a brick wall at normal walking speed. (Make a reasonable estimate of your speed and of the time it takes you to come to a stop.) Give your reasoning, and make sure your estimate has units

Answer 1

From certain assumptions that the walking speed is 2 m/s, and the stop time is 0.1 s the acceleration would be -20 m/s

Step-by-step explanation:

Using the average acceleration formula:

`a=(\Delta v)/(\Delta t)` where
`\Delta v` and
`\Delta t` are the changes in the speed and time respectively.

We have by assuming that the walking speed is 2 m/s and the stop time is 0.1s which is equal to the change in time during the stopping.

`\Delta v=v_f-v_i=0-2 m/s=-2 m/s`, where
`v_i,v_f` are the initial speed and final speed respectively, and
`\Delta t=0.1 s`

Plugging the previous in the average acceleration formula we get

`a=(-2)/(0.1)=-20\, m/s` where the minus sign indicates an acceleration in the opposite direction of the motion (or in other word opposite to the speed's direction).