SPH3U
Kinematics
Lesson #4
Uniform Motion
Remember uniform motion is when an object is moving at a constant velocity!
Speed and Velocity Problems
1.
What is the average speed of a cheetah that sprints 100 m in 4 s? How about if it sprints 50 m in 2 s?
2.
If a car moves with an average speed of 60 km/hr for an hour, it will travel a distance of 60 km. How
far will it travel if it continues this average rate for 4 hrs?
3.
A runner makes one lap around a 200 m track in a time of 25.0 s. What was the runner's average
speed? Answer: 8.0 m/s
4.
Light and radio waves travel through a vacuum in a straight line at a speed of very nearly 3.00  108
m/s. How far is light year (the distance light travels in a year)? Answer: 9.50  1015 m.
5.
*An auto travels at a rate of 25 km/hr for 4 minutes, then at 50 km/hr for 8 minutes, and finally at 20
km/hr for 2 minutes. Find the total distance covered in km and the average speed for the complete
trip in m/s. Answers: 9 km, 10.7 m/s.
6.
*If you traveled one mile at a speed of 100 miles per hour and another mile at a speed of 1 mile per
hour, your average speed would not be (100 mph + 1 mph)/2 or 50.5 mph. What would be your
average speed? (Hint: What is the total distance and total time?) Answer: 1.98 mph.
7.
*A race car driver must average 200 km/hr for four laps to qualify for a race. Because of engine
trouble, the car averages only 170 km/hr over the first two laps. What average speed must be
maintained for the last two laps?
8.
It is now 10:29 a.m., but when the bell rings at 10:30 a.m. Suzette will be late for French class for the
third time this week. She must get from one side of the school to the other by hurrying down three
different hallways. She runs down the first hallway, a distance of 35.0 m, at a speed of 3.50 m/s. The
second hallway is filled with students, and she covers its 48.0 m length at an average speed of 1.20
m/s. The final hallway is empty, and Suzette sprints its 60.0 m length at a speed of 5.00 m/s.
a.
Does Suzette make it to class on time or does she get detention for being late again?
b.
Draw a distance vs. time graph of the situation. (Assume constant
speeds for each
hallway.)
9.
During an Apollo moon landing, reflecting panels were placed on the moon. This allowed earthbased astronomers to shoot laser beams at the moon's surface to determine its distance. The
reflected laser beam was observed 2.52 s after the laser pulse was sent. The speed of light is 3.0  108
m/s. What was the distance between the astronomers and the moon?
10.
The tortoise and the hare are in a road race to defend the honor of their breed. The tortoise crawls
the entire 1000. m distance at a speed of 0.2000 m/s while the rabbit runs the first 200.0 m at 2.000
m/s The rabbit then stops to take a nap for 1.300 hr and awakens to finish the last 800.0 m with an
average speed of 3.000 m/s. Who wins the race and by how much time?