Question

seeing a police officer ahead and not being sure of the speed limit, a driver slows from 65 mi/hr to 55 mi/hr in 4.0 seconds, trying not to make it obvious. what is the cars acceleration

Answer 1

`-1.13 m/s^2`

Step-by-step explanation:

The acceleration of an object is given by:

`a=(v-u)/(t)`

where

v is the final velocity

u is the initial velocity

t is the time it takes for the velocity to change from u to v

For this problem, first we have to convert the velocities of the car from mph to m/s:

`u = 65 mi/h \cdot (1609 m/mi)/(3600 s/h)=29.1 m/s`

`v = 55 mi/h \cdot (1609 m/mi)/(3600 s/h)=24.6 m/s`

While the time interval is

t = 4.0 s

Substituting, we find the acceleration:

`a=(24.6-29.1)/(4.0)=-1.13 m/s^2`