Download Chapter 10 study guide answers

Chapter 10 Study Guide
Answer the following questions on a separate sheet of paper. Show all equations, all work and all units to receive
homework credit.
1. What is Force? What is the SI unit for Force?
Force is the push or pull on an object. SI unit = Newton
2. Define Net Force. Draw two diagrams with arrows to represent Net Force. One should show positive net force
and the other should show negative net force.
Net Force = Combination of all forces acting on an object. See textbook, pg 376-377
3. Compare the terms Balanced and Unbalanced Force. Use the word velocity in your comparison.
Unbalanced forces will cause the velocity of an object to change. Balanced forces acting on an object do not
change the object’s velocity.
4. What factors determine the strength of the friction force between two surfaces?
The strength of the force depends on the type of surfaces involved and on how hard the surfaces push
together.
5. What are the four types of Friction? Briefly describe each.
Static-acts on nonmoving object. Sliding-when two objects slide over each other. Rolling-when two objects
roll across a surface. Fluid- when solid objects move through fluids (air, water, oil)
6. What are two ways that Friction can be useful?
Static friction allows objects to remain in place. Sliding friction allows moving objects to stop to avoid
colliding with other objects.
7. What types of friction occur when you ride a bike through a puddle?
Rolling and fluid friction
8. What is the difference between weight and mass? What is the equation for finding weight?
Mass is the amount of matter in an object, weight is the force of gravity on an object. Weight = Mass x
Acceleration due to Gravity
9. What is the SI unit for weight? What is the SI unit for mass?
Weight = Newtons, Mass = Kilogram
10. How do Mass and Distance affect the force of gravity?
Gravity increases with mass and decreases with distance. Law of UniversalGravitation= objects attract
each other no matter what.
11. When gravity is the only force present, will two objects with different masses fall at the same or different rates?
Explain.
Same rates. Acceleration due to gravity is the same for all objects, regardless of mass because of Newtons’s
2nd law…Acceleration = Net Force/Mass. As mass increases, force increases…therefore the acceleration
stays at 9.8 m/s/s
12. In free fall, which force causes an object to accelerate in the downward direction?
Gravity
13. Falling objects with (greater or less) surface area experience more air resistance.
Greater
14. Air resistance is a type of ________________ friction.
Fluid Friction
15. What force changes when a sky diver’s parachute opens? What force stays the same?
Air resistance increases, but the force of gravity stays the same.
16. If one ball is dropped vertically and a second ball is thrown horizontally, which will hit the ground first? (the only
force acting on the ball is gravity)
They will hit the ground (fall) at the same time. Gravity continues to act on each ball in the same way. A
projectile is an object thrown.
17. The situation in # 16 is an example of what type of Motion?
Projectile Motion
18. Compare the terms compression and tension.
Both are types of Elastic forces. Compression is an elastic force that squeezes or pushes matter together.
Tension is an elastic force that stretches or pulls matter.
19. What is Newton’s 1st law of Motion? Include the word Inertia in your answer.
An object will remain at rest or moving at a constant velocity unless it is acted on by some outside force.
Inertia is the tendency of an object to resist change.
20. How is mass related to inertia.
The greater the mass of an object, the greater its inertia.
21. What is Newton’s 2nd law of Motion? Provide the equation for acceleration.
Acceleration depends on the net force acting on an object and the object’s mass.
Acceleration = Net Force/Mass
22. What is the net force acting on a .25 kg hockey puck accelerating at a rate of 16 m/s/s?
4 Newtons.
23. Find the acceleration of a 1200 kg car that has a net force of 5,000 N acting on it.
4.17 m/s/s
24. What is the net force required to make a 64 kg surfer accelerate at a rate of 5 m/s2?
320 Newtons
25. What net force would make the surfer in question #24 accelerate at a rate of 2.5 m/s2?
160 Newtons
26. The force of gravity causes objects to accelerate at a rate of 9.8 m/s2. What is the force of gravity on a 19 kg
bowling ball?
186.20 Newtons
27. An elephant named Leroy was gathering apples in a pile. When Leroy came back to add to the pile, a anteater
named Walter was eating the peanuts. So Leroy launched a 3.5g apple 3m in 0.8 seconds at Walter and hit him in
his long nose.
a. What was the speed/velocity of the apple?
3.75 m/s
b. If the apple was accelerating at 9m/s/s, what was the force of the apple when it hit Walter?
.03 Newtons
28. What is Newton’s 3rd Law of Motion?
When one object exerts a force on another, then the second object exerts a force of equal and opposite
strength on the first object.
29. What are Action-Reaction Pairs? Why don’t action reaction pairs cancel each other out?
Equal in strength and opposite in direction. They are acting on different objects.
30. What is Momentum? What is the equation for Momentum.
The quantity of motion. Momentum = Mass x Velocity
31. What is the Momentum of a 930 kg car moving at a speed of 30 m/s?
27,900 kg x m/s
32. Which has more momentum—a 350 shark swimming at 5 m/s or a 450 whale swimming at 2 m/s?
1750 kg x m/s (shark)…900 kg x m/s (whale) The Shark!
33. A 240 kg snow mobile travels at 16 m/s. The mass of the driver is 75 kg. What is the momentum of the
snowmobile and the driver?
240 + 75 = total of 315 kg. Momentum = Mass x Velocity. Momentum = 315 kg x 16 m/s.
5,040 kg x m/s
34. If you blow up a balloon and let it go…why does it fly forward? Draw a diagram with labels.
Action-Reaction Pairs. Newton’s 3rd law. Air from balloon pushes on air outside of the balloon. The air
outside of the balloon pushes back at the balloon.
35. What is the Law of Conservation of Momentum?
Total momentum of any group of objects remains the same, or is conserved, unless an outside force acts on
the objects.
36. Describe how the following forces are each involved in a roller coaster: Inertia, Friction, Air resistance,
Acceleration, Gravity, Gravitational Potential Energy and Kinetic Energy. You might want to draw a picture.
If a roller coaster, is standing still, it won't want to move unless some force pushes or pulls it. This
resistance of the roller coaster to move is called inertia. The more mass a body has the more inertia it has.
A motorized pully drags the roller coaster up the initial hill. Once the roller coaster is moving, it will want
to keep moving, along the direction of motion, unless something causes it to speed up or slow down. This
resistance of the moving roller coaster to changing its velocity is another example of its inertia. Again, the
greater the mass of the body, the more inertia it has.
When you ride a roller coaster a motor does the work to get you up the first hill. As the coaster is
being pulled up the hill by the motor it is storing more and more potential energy. That potential energy is
turned into kinetic energy as gravity pulls you down the first hill. The farther you go down the hill, the
more potential energy is changed into kinetic energy, which you feel as speed. The ride goes fastest at the
bottom of the hill because more and more of the potential energy has been changed to kinetic energy.
On a downhill slope or a sharp curve, a ride will probably increase in velocity or accelerate. While
moving uphill or in a straight line, it may decrease in velocity or decelerate. The force of gravity pulling a
roller coaster down hill causes the roller coaster to go faster and faster, it is accelerating. The force of
gravity causes a roller coaster to go slower and slower when it climbs a hill, the roller coaster is
decelerating or going slower. The acceleration of a roller coaster depends on its mass and how strong is the
force that is pushing or pulling it.
Coaster designers know that friction and air resistance play a part in the ride. Therefore, they
make each successive hill LOWER so that the coaster will be able to make it over each peak. Coaster
designers also take advantage of friction to slow the coaster and bring it to a safe stop when breaks are
applied at the end of the ride.