Problems

12.

The driver of a sports car traveling at 10.0 m/s steps down hard on the accelerator for 5.0 s and the velocity increases to 30.0 m/s. What was the average acceleration of the car during the 5.0 s time interval?

–1.0 × 10² m/s²
–4.0 m/s²
4.0 m/s²
1.0 × 10² m/s²

13.

A girl rolls a basketball across a basketball court. The ball slowly decelerates at a rate of −0.20 m/s². If the initial velocity was 2.0 m/s and the ball rolled to a stop at 5.0 sec after 12:00 p.m., at what time did she start the ball rolling?

0.1 seconds before noon
0.1 seconds after noon
5 seconds before noon
5 seconds after noon

14.

A swan on a lake gets airborne by flapping its wings and running on top of the water. If the swan must reach a velocity of 6.00 m/s to take off and it accelerates from rest at a constant rate of 0.350 m/s², how far will it travel before becoming airborne?

−8.60 m
8.60 m
−51.4 m
51.4 m

15 .

A swimmer bounces straight up from a diving board and falls feet first into a pool. She starts with a velocity of

4.00 m/s

and her takeoff point is

8 m

above the pool. How long are her feet in the air?

$0.408 s$
$0.816 s$
$1.34 s$
$1.75 s$
1.28 s