Question

A skydiver slows down from 54 m/s to 4 m/s by opening his parachute. this change takes 0.75 seconds. what is the skydiver's acceleration

Answer 1

The acceleration of the skydiver is given by:
$a= \frac{v_f-v_i}{t}$
where
$v_f=4 m/s$ is the final velocity of the skydiver
$v_i=54 m/s$ is the initial velocity of the skydiver
$t=0.75 s$ is the time taken for the change of speed

Substituting the numbers into the equation, we find the skydiver's acceleration:
$a= \frac{4 m/s-54 m/s}{0.75 s} =-66.7 m/s^2$
where the negative sign means it is a deceleration.