15 points- due _______________
Name: _____________________________Hr.___
The test
70 points = 1 short answer question from list (5 pts.), questions from the video (5 pts.), and problems (60 pts.)
Topics covered:
Circular motion (Ch. 7, sec.3)
Gravitation (Ch. 7, sec. 3)
Centripetal force (Ch. 7, sec. 2 & 3)
Pendulums (part of Ch.12, sec. 2)
Possible Short Answer Questions (There will be one for these questions for 5 points on the test.)
# 1 Explain the difference between centripetal and centrifugal force. Give an example of when each occurs.
# 2 Explain and show how we derived the pendulum equation.
# 3 What is the Universal Law of Gravitation? Give an example of when it can be used.
# 4 Explain and show how we got the equation for “g” at any altitude.
# 5 Explain and show how we found the equation for the speed of a satellite.
Make sure you understand all the questions and problems on:
The “When Pigs Fly” Mini Lab and Problems (pink)
Pendulum Lab (white)
Gravitation Notes (white)
“If We Had No Moon” video questions (white)
Gravity Problems (blue)
this review
Summary of what you need to know:
I) Circular Motion
v = 2πr/T
ac = v2/r
Fc = mac
Fc = mv2
r
II) Gravitation
Fg= mg
Fg = Gm1 m2 , G = 6.67 x 10-11 Nm2
kg2
r2
Uses:
i) how to find g any distance
from any object
III) Pendulums
T2 = 4π2l
g
ii) speed needed to keep an
object in orbit
iii) find the altitude of orbiting object
if you know its speed
REVIEW ASSIGNMENT- Do this assignment on separate paper.
I) Circular Motion and Centripetal Force.
1.
2.
3.
4.
5.
6.
a. Explain the difference between “Δt” and “T.”
b. Explain the difference between centripetal force and centrifugal force.
Calculate the speed in miles per hour that we travel around the sun if the average radius is
1.5 x 1011 m. (ans. about 66,870 mph)
If you are riding on a merry-go-round that suddenly goes out of control. You are traveling so
fast that you can no longer hold on. Sketch the path you will take as you fly off and explain why.
Calculate the centripetal force acting on you (mass 60 kg) if you are driving in a circle with a circumference
of 40 m and it takes you 47 seconds to drive around that circle ten times. (ans. 683 N )
You (mass 65kg) are at a NASA training center preparing to handle g-forces in space. You get inside a
capsule with a radius of 3 meters that spins in a plane that is parallel to the floor. If you spin at 35
miles per hour, how many g’s will you experience? (ans. 8.3 g’s)
Explain how to calculate the minimum speed you needed to spin a bucket over your head so
the water does not spill out. Calculate the minimum speed if the radius is 0.95 meters. Explain
one other situation where it is important that an object spinning upside down does not fall out.
(ans. 3.05 m/s)
II) Gravitation
7. What is the Universal Law of Gravitation? Explain it, including the equation.
8. Calculate the gravitational force of attraction between the earth and the moon. (The earth and the moon
are at a mean distance of 3.8 x 108 m apart. The distance includes the radius already!)
(ans. 2.03 x 1020 N)
9. Show and explain why all objects fall to the earth with the same acceleration. Calculate that
acceleration using Newton’s 2nd Law and the Universal Law of Gravitation.
10. a. What happens to the acceleration due to gravity as you go further away from the earth?
b. Calculate your weight in pounds if you were 350 miles above the earth’s surface if you weigh
143 lbs. on the earth’s surface. Show where your equation comes from. (ans. 121 lbs.)
11. a. Explain and show how we came up with the equation for the speed of a satellite.
b. Calculate the velocity a satellite must have in order to maintain an altitude of 1,500,000 m above the
earth’s surface. (ans. 7,119 m/s)
12. Calculate your weight in Newtons if you were 500 miles above the surface of Jupiter
(mass 1.9 x 1027 kg, diameter 142,984 km). You can assume your mass is 65 kg. (ans. 1,576 N)
13. Explain what the vomit comet is and how it flies in order to create the fun ☺.
14. Calculate the altitude in miles above the earth’s surface of a satellite if it is falling around the earth at
15,500 miles per hour. (ans. about 1,200 miles)
III) Pendulums
15. What variable(s) affect(s) the period of a pendulum? Explain what you did in the pendulum lab and
show how to get the equation for the motion of a pendulum.
16. A friend bets you that you can’t make a pendulum with a period of exactly one second. What
length would you make it and how much mass would you attach to the end of it? Show your
calculations. (ans. 0.25 m, doesn’t matter)
17. a. We know the acceleration due to gravity on the moon is 1/6th of what it is on the earth. Prove this by
calculating the acceleration due to gravity on the moon using a variation of the Universal Law of
Gravitation. (ans. 1.62 m/s2)
b. Find the length of a pendulum oscillating on the moon that would have the same period as a 1.0-m
pendulum oscillating on Earth. (ans. 0.17 m)