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Chapter 9 and 10 - Study Guide - Key
1. A
force
is a push or a
pull.
These can result from
actions such as twisting, ___squeezing, stretching__ and ___bending_.
2. What do you call the sum of all of the forces acting on an object?
The net force.
3. Describe the difference between a balanced and unbalance force.
Balanced forces are equal but in opposite directions so there is no motion as a
result, while unbalanced forces are unequal which cause an object to move.
4. When an object resists a change in it motion, this is called____inertia______.
5. Give one example of question #4 that can happen when you ride in a car that stops
suddenly. Your body’s inertia makes you keep moving forward at the same
speed the vehicle was traveling at before you stopped.
6. What is Newton’s 1st Law of Motion?
The Law of Inertia: an object will resist any change in its motion.
7. What is Newton’s 2nd Law of Motion?
Force equals mass x acceleration
8. What is Newton’s 3rd Law of Motion?
For every action, there is an equal and opposite reaction.
9. What do you call the force that is caused by two surfaces rubbing against each
other? Friction
10. What two things does friction depend on?
1. the type of surface (texture)
2. how hard the surfaces are pushed together
11. Friction __opposes_____ motion, causing moving objects to
___stop___________.
12. Name three types of friction and give one example for each:
1. Sliding friction
ex: striking a match
2. rolling friction
ex: tires on a road
3. fluid friction
ex: air resistance
13. What force pulls objects toward other objects such as the Earth, the Moon, or the
Sun?
The force of gravity
14. How fast do objects in freefall accelerate towards Earth?
9.8 m/s2
15. Eventually objects falling towards Earth will stop accelerating because of
__air_________ __resistance___________________.
16. The answer to #15 depends on the __size__________, ___shape_____, and
___speed____ of an object.
17. The top speed an object like a sky diver reaches while falling is called
__terminal_______ _____velocity_____.
18. What two forces are equal when the answer to #17 is reached?
gravity and air resistance (fluid friction)
19. What lowers the terminal velocity of a skydiver so they can land safely?
a parachute
20. Describe the difference between weight and mass.
Weight is the amount of force that gravity has on an object and mass is the
measure of how much matter is in an object.
21. What states that the force of gravity exists between all objects in the universe?
The Law of Universal Gravitation
22. The Moon’s gravity is ____1/6__________ that of Earth.
23. Give two examples of Newton’s 3rd Law (these are not in your notes….think
about the Newton Vehicle Project).
1. a rocket pushes air downward, the surrounding air pushes it up
2. tires on a car push backward and the floor pushes forward.
24. How do you figure out the momentum of an object?
momentum (p) = mv
25. Can a golf ball and an elephant have the same momentum? Explain.
p = mv, so a golf ball at a high enough velocity could have the same amount
of momentum as a very slow moving elephant.
26. What does it mean to say that momentum is conserved after two pool balls hit
each other? (hint: compare their momentum before and after the collision)
It means the momentum of the balls before they make contact will remain
the same even after they hit each other.
Be sure to (1) ALWAYS write the equation, (2)plug in the numbers and units,
and (3) give the answer with the correct units.
27. An ant can travel approximately 30 meters per minute. How many meters could
an ant move in 45 minutes?
d = st
d = (30m/min)(45 mins)
d = 1,350 m
28. How much time would it take for the sound of thunder to travel 2000 meters if
sound travels a the speed of 330 m/s ?
t=d÷s
t = (2000 m) ÷ (330 m/s)
t = 6.06 s
29. Calculate the average speed (in meters/sec) if a Cheetah runs 140 meters in 5
seconds.
s=d÷t
s = (140 m) ÷ (5 s)
s = 28 m/s
30. The Indy-500 race car then slows from 36 m/s to 15 m/s over 3.0 s. What is the
acceleration over this time interval?
a = (Vf - Vi) ÷ t
a = (15 m/s – 36 m/s) ÷ 3.0 s
a = - 7 m/s2
31. An Indy-500 race car’s velocity increases from 4.0 m/s to 36 m/s over a 4 s
period. What is the acceleration?
a = (Vf - Vi) ÷ t
a = (36 m/s – 4m/s) ÷ 4.0 s
a = 8 m/s2
32. A man hits a golf ball (0.2 kg) which accelerates at a rate of 20 m/s2. What
amount of force acted on the ball?
F = ma
F = ( .2kg)(20 m/s2)
F=4N