Physics Review Question
Unit: mechanics
Year: 1994 Question#: 9
Question: A car is traveling at a constant speed of 14 m/s along a
straight highway. A tree and a speed limit sign are behind a highway. As it passes a tree,
the car starts to accelerate. the car is accelerated uniformly at 2.0 m/s2
until it reaches the speed limit sign, 5.0 sec. later.
9. When the car reaches the sign, the car's speed is
(1 ) less than the speed limit
(2 ) greater than the speed limit
(3 ) egual to the speed limit
What is this question really asking?
Explanation by: Danny A
[ Return to question menu ]
Answer 1
less than the speed limit
CORRECT
If the car was going 14m/s and it started to speed up at 2m/s2 for 5 seconds
that means the total speed increased 10m/s (using the formula
) which you add to 14m/s which equals 24m/s. return
to top
Answer 2
greater than the speed limit
INCORRECT
If it was going for 6 seconds this would be correct. Try using 
to find the change in velocity then add it to the inital velocity.
return to top
Answer 3
equal to the speed limit
INCORRECT
if it was going for 5.5 seconds than this answer would be correct.
Try using 
to find the change in velocity
then add it to the inital velocity. return to top
What's this question really asking?
What is the car's speed after accelerating at 2m/s for 5s, if it started out going 14m/s
by the time it reaches the sign? return to top
