Question

Exercise 1:
A car traveling at 12 m/s slows down at a constant rate
for 4 seconds until it stops. What is its acceleration?
Exercise 2:
A runner covers the last straight stretch of a race in 4 s.
During that time, he speeds up from 5 m/s to 9 m/s.
What is the runner’s acceleration in this part of the
race?
Exercise 3:
A pebble fell from a bridge to the water below. The
pebble entered the water at a speed of 19.6 m/s. How
long did it take the pebble to reach the water from the
bridge?
Exercise 4:
Josh rolled a bowling ball down a lane in 2.5 s. The ball
traveled at a constant acceleration of 1.8 m/s2 down the
lane and was traveling at a speed of 7.6 m/s by the time
it reached the pins at the end of the lane. How fast was
the ball going when it left Tim’s hand?
Exercise 5:
How long does it take a jet to accelerate from 200 m/s
to 300 m/s with a constant acceleration of 50 m/s?

Answer 1

Exercise 1
a = (v − v0)/t = (0 − 12) / 4 = −3.0 m/s² (deceleration of 3.0 m/s²).

Exercise 2
a = (9 − 5) / 4 = 1.0 m/s².

Exercise 3
Using v = g t with v = 19.6 m/s and g = 9.8 m/s²:
t = 19.6 / 9.8 = 2.0 s.

Exercise 4
v0 = v − a t = 7.6 − (1.8)(2.5) = 7.6 − 4.5 = 3.1 m/s.

Exercise 5
Assuming acceleration is 50 m/s²:
t = (300 − 200) / 50 = 2.0 s.