Download Uniform Circular Motion HW

Name:___________________________
Period:____
Homework – Circular Motion
Help with the following vocabulary and problems can be found in the textbook, McGraw-Hill Physics, Chapter 6,
Section 2, Circular Motion. Answer the following questions using the GUESS method. (Use g=10m/s2)
1. An air puck of mass m = 0.025 kg is tied to a string and allowed to revolve in a circle of
radius r = 1.0 m on a frictionless horizontal surface. The other end of the string passes
through a hole in the center of the surface, and a mass M = 1.0 kg is tied to it, as shown the
right. The suspended mass remains in equilibrium while the puck revolves on the surface.
a. Calculate the magnitude of the force acting on the puck that maintains circular motion.
(Answer FT = 10 N)
b. Calculate the linear speed of the puck. (Answer v = 20 m/s)
2. A 0.013 kg rubber stopper is attached to 0.93 m length of string. The stopper is swung in a horizontal circle,
making one revolution in 1.18 s.
a. Find the speed of the stopper. (Answer v= 5.0 m/s)
b. Find its centripetal acceleration. (Answer a =27 m/s/s radially inward)
c. Find the force the string exerts on it. (Answer FT =0.35 N radially inward)
3. Horizontal Circle - An Olympic hammer is being swung in a (clockwise or counterclockwise) horizontal circle. To
the right is a top view of this action. Draw and label the velocity, centripetal acceleration and
net force vectors on the diagram at position(s) (A, B, C, D).
4. Suppose in the example above, an athlete whirls a 7.00 kg hammer tied to the end
of a 1.3 m chain in horizontal circle. The hammer makes one complete revolution
in 1.0 s.
a. What is the centripetal acceleration of the hammer? (51 m/s2)
b. What is the tension in the chain? (360 N)
Homework – Circular Motion (continued)
5. A string that is 0.65 m long exerts a centripetal force of 11.6 N on a 0.10 kg yo-yo that is whirling on the end of
the string. What is the velocity of the yo-yo? (8.7 m/s)
6. A remote controlled car moves around a curve at a velocity of 1.5 m/s and a centripetal acceleration of 3.6
m/s2. What is the radius of the curve? (0.63 m)
7. A 0.10 kg mass is attached to a string 75 cm long and revolves in a horizontal circle, once every 0.80 s.
a. What is the centripetal acceleration of the mass? (46 m/s2)
b. What is the tension in the string? (4.6 N)
8. Norman Neutron swings a rubber ball attached to a string over his head in a horizontal, circular path. The piece
of string is 1.5 m long and the ball makes 120 complete turns each minute.
a. What is the average velocity of the ball? (19 m/s)
b. What is the ball’s centripetal acceleration? (240 m/s2)
9. What is the centripetal acceleration of a point on the perimeter of a bicycle wheel of diameter 70. cm when a
bike is moving at 8.0 m/s? (180 m/s2)
10. A steel beam is rotated in a horizontal plane to provide the centripetal acceleration for training pilots. If the
pilot sits 2.0 m from the center of rotation, at what speed must he rotate to experience a horizontal centripetal
acceleration of 78 m/s2? (12 m/s)
Homework – Circular Motion (continued)
11. Roxanne is making a strawberry milkshake in her blender. A tiny, 5 g strawberry is rapidly spun around the
inside of the container with a speed of 14.0 m/s, and experiences a centripetal force of 10.0 N. Calculate the
radius of the blender. (Answer: r = 0.098 m)
12. A 95-kg halfback makes a turn on the football field. The halfback sweeps out a path which is a portion of a circle
with a radius of 12-meters. The halfback makes a quarter of a turn around the circle in 2.1 seconds. Determine
the speed, acceleration and net force acting upon the halfback. (9 m/s, 6.8 m/s2, 650 N)
13. A 900.-kg car moving at 10.0 m/s takes a turn around a circle with a radius of 25.0 m. Determine the
acceleration and the net force acting upon the car. (4.0 m/s2, 3600 N)
14. The maximum force a pilot can stand is about seven times his weight. (This is his normal force.) What is the
minimum radius of curvature that a jet plane’s pilot, pulling out of a vertical dive, can tolerate at a speed of
250. m/s? (1040 m)
15. A 1.50-kg bucket of water is tied by a rope and whirled in a circle with a radius of 1.00 m. At the top of the
circular loop, the speed of the bucket is 4.00 m/s. Determine the acceleration, the centripetal force and the
perceived weight (i.e., the tension). (16.0 m/s2, 24.0 N, 9.00 N)
16. A pilot makes an outside loop (in which the center of the loop is beneath him) of radius 3200 m. At the top of
his loop his normal force is only one-half his normal weight. How fast is he going? (219 m/s)
Homework – Circular Motion (continued)
17. A 1.50-kg bucket of water is tied by a rope and whirled in a circle with a radius of 1.00 m. At the bottom of the
circular loop, the speed of the bucket is 6.00 m/s. Determine the acceleration, the centripetal force and the
perceived weight. (36 m/s2, 54.0 N, 69.0 N)
18. Compute the centripetal acceleration of an object on the equator. Use an equatorial radius of 6400 km. The
Earth makes one revolution in a day. (1 km = 1000 m) (0.034 m/s2)
19. Calculate the centripetal acceleration of the Earth towards the Sun. (r = 1.5 x 1011 m) (0.0060 m/s2)