Question

Tommy was walking at a rate of 4 miles hour at noon and at 12:30 pm he was walking at a brisk rate of 6 miles hour . Two hours later Tommy was walking at a leisurely rate of 2 miles hour . Which statement about Tommy's accleration is true?
A) Tommy had an accleration of zero the entire time.
B) Tommy had a positive acceleration between noon and 12:30 pm.
C) Tommy had a positive acceleration between 12:30 and 2:30 pm.
D) Tommy had a negative acceleration between noon and 12:30 pm.

Answer 1

Answer: B) Tommy had a positive acceleration between noon and 12:30 pm.

Answer 2

Answer:

B) Tommy had a positive acceleration between noon and 12:30 pm.

Explanation:

Acceleration is defined as the rate of change of velocity:

$a=\frac{v-u}{t}$

where

v is the final velocity

u is the initial velocity

t is the time

In the problem,

- At noon, Tommy is walking at a velocity of 4 mi/h

- At 12.30 pm, Tommy is walking at a velocity of 6 mi/h

- A time of half an hour (0.5 h) passed between the two moments

So Tommy's acceleration is

$a=\frac{6 mi/h-4 mi/h}{0.5 h}=4 mi/h^2$

and the acceleration is positive, since the velocity has increased.