Name: ___________________________
Section: ____
Date: ____/____/____
614
Circular Motion/Centripetal Force
1. Moving in Circles
Imagine you are riding a carousel (a merry-go-round) in a circle at a constant speed.
a. Is your velocity changing? Use the definition of velocity to support your answer.
b. Are you accelerating? Use the definition of acceleration to support your answer.
c. Must there be a net force acting on you? Use Newton’s 1st Law of Motion to support
your answer.
2. A planet orbits around the Sun (NTS*). The planet Mercury swings around the Sun.
The arrow represents the force that keeps Mercury in its orbit. (* NTS means “Not To Scale”)
A. What object or thing keeps the planet
moving in a circle?
B. What kind of force (e.g. friction, gravity,
drag, spring, normal, etc.) does this object
exert on the planet?
3. Sphere on a string. Imagine swinging a sphere on a string over your head.
A. What object or thing keeps the sphere moving in a
circle?
B. What kind of force (e.g. friction, gravity, drag, tension,
spring, normal, etc.) does this object exert on the
sphere?
Standard(s): 1.8
TA: ________
Independence Level: __________%
Assistance, coaching, prompting: _________________________________________________
4. Bowling Ball. Alan pushes the bowling ball so that it moves at a constant velocity.
David has a mallet, which he will use to hit the bowling ball so that it moves in a circle.
http://www.pbslearningmedia.org/asset/lsps07_int_circmotion/
A. Predict: Draw an arrow on each ball to B. After watching the video, draw an
show the direction David needs to hit
arrow on each ball to show the
the ball in to make it move in a counterdirection David hit the ball.
clockwise circle.
5. Car Turning a Curve. The arrows represent the force that keeps the car going around
the curve (instead of going in a straight line).
A. What object or thing keeps the car going around
the curve?
B. What kind of force (e.g. friction, gravity, drag,
tension, spring, normal, etc.) does this object
exert on the car?
6. What Do They Have in Common?
In each of these examples, there is a force that keeps the object moving in a circle.
In each case, what is similar about the direction of the force?
 If a force makes something move in a circle (or in
curve), we call it a centripetal force
 The centripetal force always points towards the
center of the circle
 The centripetal force isn’t a special/specific force
like gravity, friction, normal, tension, etc; those are
all caused by something specific.
material modified from: http://paer.rutgers.edu/pt3/experimentindex.php?topicid=5&cycleid=9,
http://www.pbslearningmedia.org/resource/lsps07.sci.phys.maf.circmotion/circular-motion/
What happens if the Centripetal Force is removed?
7. Ball in Ring Frame: A wooden ball is placed inside a large metal ring placed on a flat
surface, and set in motion inside of the ring. Part of the ring can be removed, making a
gap and allowing the ball to escape from the ring.
A. Predict: Which path do you think the B. After watching the video, which path
ball will take when it escapes the
did the ball will take when it escaped
ring?
the ring?
A
A
B
B
C
D
C
D
C. After the centripetal force is removed, the ball moves in a straight line. Why do you
think this happens? (Hint: Think back to Newton’s 1st Law of Motion—The Law of
Inertia)
8. Tetherball. A tetherball swings around in a circular path, as shown.
A. There are two major forces acting on the ball. Draw
them in and label them according to type.
B. Neither of these forces points to the center of the
circular path followed by the tetherball. Can the net
force be the centripetal force?
material modified from: http://paer.rutgers.edu/pt3/experimentindex.php?topicid=5&cycleid=9,
http://www.pbslearningmedia.org/resource/lsps07.sci.phys.maf.circmotion/circular-motion/
Central Concept: Newton’s laws of motion and gravitation describe and predict the motion of most
objects.
1.8 Describe conceptually the forces involved in circular motion.
MCAS Questions:
material modified from: http://paer.rutgers.edu/pt3/experimentindex.php?topicid=5&cycleid=9,
http://www.pbslearningmedia.org/resource/lsps07.sci.phys.maf.circmotion/circular-motion/
material modified from: http://paer.rutgers.edu/pt3/experimentindex.php?topicid=5&cycleid=9,
http://www.pbslearningmedia.org/resource/lsps07.sci.phys.maf.circmotion/circular-motion/