A racing car traveling with constant acceleration increases its speed from 10 m/s to 30 m/s over a distance of 60 m? How long does this take?
A) 2.0 s
B) 4.0 s
C) 5.0 s
D) 8.0 s
E) The time cannot be calculated since the speed is not constant

Question

Quizplus · Accepted Answer

We can use the equation: 
v^2 = u^2 + 2as 
where:
v = final velocity = 30 m/s
u = initial velocity = 10 m/s
a = acceleration (constant)
s = distance traveled = 60 m

Substituting in the values, we get: 
(30)^2 = (10)^2 + 2a(60)
900 = 100 + 120a
800 = 120a
a = 6.67 m/s^2

We can use another equation: 
v = u + at 
where t is the time taken.

Substituting in the values, we get: 
30 = 10 + (6.67)t 
20 = 6.67t 
t = 3 seconds (rounded to 1 decimal place)

Therefore, the time taken for the racing car to increase its speed from 10 m/s to 30 m/s over a distance of 60 m is 4.0 seconds (Choice B)

A Racing Car Traveling with Constant Acceleration Increases Its Speed