Question

A car travels on a straight, level road. (a) Starting from rest, the car is going 38 ft/s (26 mi/h) at the end of 4.0 s. What is the car's average acceleration in ft/s2? (b) In 3.0 more seconds, the car is going 76 ft/s (52 mi/h). What is the car's average acceleration for this time period?

Answer 1

`a)9.5(ft)/(s^2)\\ b) 12.66(ft)/(s^2)`

Step-by-step explanation:

A body has acceleration when there is a change in the velocity vector, either in magnitude or direction. In this case we only have a change in magnitude. The average acceleration represents the speed variation that takes place in a given time interval.

a)

`a_(avg)=(\Delta v)/(\Delta t)\\a_(avg)=(v_(f)-v_(i))/(t_(f)- t_(i))\\a_(avg)=(38(ft)/(s)-0)/(4 s- 0)=9.5(ft)/(s^2)\\`

b)

`a_(avg)=(\Delta v)/(\Delta t)\\a_(avg)=(v_(f)-v_(i))/(t_(f)- t_(i))\\a_(avg)=(76(ft)/(s)-38(ft)/(s))/(7 s- 4s)\\a_(avg)=(38(ft)/(s))/(3s)=12.66(ft)/(s^2)`