Question

A powerful missile reaches a speed of 5 kilometers per second in 10 seconds after its launch. What is the average acceleration of the missile during this period?

a) 0.2 meters/second^2
b) 0.4 centimeters/second^2
c) 0.5 meters/second^2
d) 0.5 kilometers/second^2

Answer 1

Average acceleration  =  (change in speed)  /  (time for the change)

The missile's change in speed is  (5,000 - 0)  =  5,000 m/s

Average acceleration  =  (5,000 m/s)  /  (10 sec)

                                 =      500 m/s²       (about  51 Gs)

Inconveniently, this isn't one of the choices on the list. Is there something wrong, either with the choices or with my solution ?

No. Relax. Everything is OK.

500 meters is the same thing as 0.5 kilometer.  So my answer can also be written as  0.5 km/s² .  That doesn't change anything, and it IS one of the listed choices.

The average acceleration is 0.5 km/sec²  (d) .

Answer 2

Average acceleration is the change in velocity divided by an elapsed time.  So, we can calculate it as follows:

acceleration = 5 - 0 / 10 - 0 = 0.5 kilometers/second^2

Therefore the correct answer is option D.

Hope this answers the question. Have a nice day.