1. Unit 4, Lesson 4: Circular Motion Practice

2. Question 1 An empty 22 kg seat on a swing-type ride at
the fairgrounds has a kinetic energy of 480 J.
a) What is the centripetal force on the empty seat?
b) Find the angle the rope makes with vertical.
Answers: 140 N, 32 degrees
20 min

3. Question 2
Montanna decides to try out the new Fast and Furious Ferris Wheel at Calaway Park, which has a radius of 16 m. The ride rotates 5 times every minute. Find the force exerted by the seat against Montanna (40 kg) when the she is
a) at the top of the ride
b) at the bottom
c) at a point halfway between the top and bottom (i.e. at “3 o-clock”)
Answers:
a) 217 N
b) 567 N
c) 430 N, 66 degrees upward
20 min

4. Question 3
Patrick decides to impress the cowgirls at this year’s Calgary stampede by showing off his lasso skills. He whirls a 2-kg stone attached to a rope in a horizontal circle of radius 40 cm. The string makes an angle of 30° with the vertical. Find the tension in the rope and the speed of the stone.
Answer: N, 1.51 m/s
20 min

5. Homework:
Do #1 and 2 on pg. 104 of your textbook.

6. Unit 4, Lesson 5: More Circular Motion Practice

7. Question 4
A penny is placed on a record that is gradually accelerated to 78 rpm. The penny stays on the record if it is placed within 8 cm of the center. What is the coefficient of friction between the penny and the record?
Answer: 0.544

8. Question 5
Flying a plane, Damian comes out of a vertical dive in a circular arc such that his upward acceleration is 9g. (a) If his mass is 50kg, what is the magnitude of the force exerted by the seat on him at the bottom of the arc? (b) If the speed of the plane is 320 km/h, what is the radius of the circular arc?
Answers:
a) 4900 N
b) 90 m

9. Question 6
Jordon starts from rest on his skis at height H above the center of a rounded hummock of radius 4.0 m. There is negligible friction. Find the maximum value of H for which Jordon remains in contact with the snow at the peak of the hummock.
Answer: 6.0 m

10. Homework:
Do #3 and 4 on pg. 104 of your textbook.