Question

A car moves in a straight line at 20.0 m/s for 12.0 miles, then at 30.0 m/s for another 12.0 miles.

Answer 1

What is the question being asked

Answer 2

Answer:

(a). The average speed less than 25.0 m/s.

(b). The  car's average speed is 24 m/s.

Explanation:

Given that,

Speed v= 20.0 m/s

Distance d= 12.0 miles

Speed v'= 30.0 m/s

Distance d'=12.0 miles

We need to calculate the time for first 12 miles distance

Using formula of time

$v=\dfrac{d}{t}$

$t = \dfrac{d}{v}$

$t=\dfrac{12.0}{20.0}$

$t=0.6\ sec$

We need to calculate the time for another 12 miles distance

Using formula of time

$t=\dfrac{12.0}{30.0}$

$t=0.4\ sec$

We need to calculate the average speed

$v_{avg}=\dfrac{D}{T}$

Where, D = total distance

T = total time

Put the value into the formula

$v_{avg}=\dfrac{12.0+12.0}{0.6+0.4}$

$v_{avg}=\dfrac{24.0}{1.0}$

$v_{avg}=24\ m/s$

The average speed less than 25.0 m/s.

(b). The  car's average speed is 24 m/s.

Hence, This is the required solution.