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Chapter 4 CPO
| term/question | definiton/answer |
|---|---|
| Name 3 ways in which forces are created. | Muscles, moving matter, massive objects,gravity |
| If you drop a feather and a baseball in a place where there is no air (a vacuum), how will their motions compare? Why? | They'll fall at the same rate because there is no gravity to make each object possess weight. |
| Name the four fundamental forces of nature, the forces from which all others are created. | Strong nuclear force, electromagnetic force, weak force, and gravity. |
| Forces cause changes to the motion of objects. Name a force and describe two changes it makes. Answers may vary. | When a soccer ball is coming your way kicking it requires a force. The kicking changes the ball's speed from fast to slow to fast and the direction it is going in from you to your teammate/ the goal. |
| What information do you need to describe a force? | Strength and direction. |
| Write a formula expressing the relationship between weight and mass. Explain the difference between weight and mass. | w=mg Weight is a force caused by mass and changes depending on gravity. Mass is a fundamental property of matter and does not change because of gravity. |
| Identify which of the following are units of force (F) and which are units of mass (M). a. ____ kilogram c. ____ pound b. ____ newton d. ____ gram | a. mass b. weight c. weight d. mass |
| What happens to a spring’s force if you stretch it more? | The tension grows and the force of the spring going back will be greater. |
| The value of “g” is different on Earth and the Moon. a. What are the values of “g” on Earth and the Moon? b. How does the strength of gravity affect the mass and weight of objects measured on Earth and the Moon? | a. Earth= g Moon = 1/6g b. The more gravity (the stronger the pull), the heavier one's weight will be. |
| How are force vectors represented? (IMPORTANT) | Using arrows on a coordinate plane. The thickness of the arrows represent the strength , the angle represents the direction, and the length of the arrow represents the amount of newtons. |
| Does it require more force to start an object sliding or to keep it sliding? Explain your answer. (IMPORTANT) | It takes more to get it moving because static friction is almost always greater than sliding friction at slow speeds. |
| Explain why ice generally has very little friction when it is in contact with other materials. | There is a thin layer of water between the two substances. Ice tends to be smoother w/ water. |
| Explain how friction keeps a nail in place in a block of wood. If you try to pull out the nail, which way does the friction act? | The wood pushes against the nail on all sides. The friction goes downward (the opposite direction). |
| What way does friction go? | The opposite direction of the object's direction. |
| Name two types of energy generated by friction and give an example of each. | Mechanical, wear, heat, and motion. Rubbing your hands together to make them warm is an example of heat and motion energy. |
| Why is it much easier to slide a cardboard box when it is empty compared to when it is full of heavy books? (IMPORTANT) | The more weight there is, the more friction there is. |
| Explain two ways friction can be reduced. (IMPORTANT) | Ball bearings, lubricants (like oil), thin layer of water, air cushion. |
| Is friction something we always want to reduce? Explain. (IMPORTANT) | We don't want to always reduce friction because we need tires to brake and tires to grip the road. |
| Standing on Earth, gravity exerts a downward force on you. a. What other force acts on you? b. What is the direction of the other force? c. What do you know about the magnitude, or strength, of this other force? | a. normal force b. upwards c. it has the same amount of force as the weight pushing down |
| If the net force on an object is zero, can the object be moving? Explain. (IMPORTANT) | Yes it just needs to be moving at a constant velocity. Meaning, it should be moving at a constant speed and direction. |
| Describe the motion of the race car shown in the figure to the right. Is it speeding up or slowing down? (look in spiral) (IMPORTANT) | Slowing down because the drag is greater than the thrust |
| What four main forces act on an airplane in flight? If the plane accelerates forward, which two forces must be out of balance? To fly on a level path, which two forces must be in balance? | Weight, drag, thrust, and lift. Drag and thrust must be out of balance to accelerate. Weight and lift must be in balance to fly levelly. |
| Which of the following diagrams correctly shows the normal force on the block of wood sliding down the incline? | A. The on with the arrow straight down and the block slanted. |
| Draw a free-body diagram for the forces acting on the parachutist shown. Don't forget about air friction! | A parachute man with an arrow pointing up with 750 N and an arrow down with 800 N |
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