Matter in Motion Chapter 5 Section Review Pg 111 #1-4, pg 114 #1-3, pg 118 #1-3, pg 124 #1-4, pg 129 #1-3

Pg 111 #1-4 1. What is a reference point? An object that appears to stay in place in relation to an object being observed and is used to determine if the object is in motion. 2. What two things must you know to determine speed? The distance traveled and the time taken to travel that distance

Pg 111 #1-4 (cont.) 3. What is the difference between speed and velocity? Speed does not include direction; velocity does. 4. Explain why it is important to know a tornado’s velocity and not just its speed. It is important to know the velocity because velocity includes direction. Knowing only the speed would not tell the direction that the tornado is traveling. Knowing the direction of travel would allow people to avoid or escape it’s path.

Pg 114 # 1-3 1. What is acceleration? Acceleration is the rate at which velocity changes. 2. Does a change in direction affect acceleration? Explain your answer. Yes, a change in direction does affect acceleration. Acceleration is a measure of velocity change. Velocity is speed in a given direction, and velocity changes if direction changes.

Pg 114 #1-3 (cont.) 3. How do you think a graph of deceleration would differ from the graph shown above? Explain your answer. The graph showing acceleration has a positive slope. A graph showing deceleration would have a negative slope. The graph would take this shape because velocity would be decreasing as time passes.

Pg 118 #1-3 1. Give four examples of a force being exerted. Kicking a ball, writing with a pencil, pulling a rope, pushing a stalled car. 2. Explain the difference between balanced and unbalanced forces and how each affects the motion of an object. Unbalanced forces occur when the net force on an object is not zero; balanced forces occur when the net force equals zero. Unbalanced forces cause a change in an object’s motion; balanced forces cause no change.

Pg 118 #1-3 (cont.) 3. In the picture at left, two bighorn sheep push on each other’s horns. The arrow shows the direction the two sheep are moving. Describe the forces the sheep are exerting and how the forces combine to produce the sheep’s motion. Because the sheep are moving as indicated by the arrow, the forces they are exerting on each other are unbalanced. The sheep on the left is exerting a larger force, so the total net force is in the direction it is pushing.

Pg 124 #1-4 1. Explain why friction occurs. Friction occurs because the microscopic hills and valleys of the two touching surfaces “stick” to each other. 2. Name two ways in which friction can be increased. Friction can be increased by making surfaces rougher and by increasing the force pushing the surfaces together.

Pg 124 #1-4 (cont.) 3. Give an example of each of the following types of friction: sliding, rolling, and fluid. Sliding – skiing and writing with a pencil; rolling – riding a bicycle and pushing a handcart; fluid – swimming and throwing a softball. 4. Name two ways that friction is harmful and two ways that friction is helpful to you when riding a bicycle. Harmful – it causes tire tread to wear down and the wind can slow you down; helpful – the wheels grip the road and your feet and hands stay on the pedals and handlebars.

Pg 129 #1-3 1. How does the mass of an object relate to the gravitational force the object exerts on other objects? The greater an object’s mass, the larger the gravitational force it exerts on other objects. How does the distance between objects affect the gravity between them? As the distance between objects increases, the gravitational force between them decreases; as the distance between objects decreases, the gravitational force between them increases.

Pg 129 #1-3 (cont.) 3. Explain why your weight would change if you orbited Earth in the space shuttle but your mass would not. A person’s weight decreases in orbit because the distance between the person and the Earth would increase. But the person’s mass would remain the constant, because mass is the amount of matter in an object, and it does not depend on gravitational force.