Physical Science: Module 10 Study Guide
Terms in this set (21)
the tendency of an object to resist any change in its velocity
A force that opposes motion, resulting from the contact of two surfaces
Friction that opposes motion once the motion has already started
Friction that opposes the initiation of motion
Newton's First Law
An object in motion (or at rest) will tend to stay in motion (or at rest) until it is acted upon by an outside force
Newton's Second Law
When an object is acted on by one or more outside forces, the total force is equal to the mass of the object times the resulting acceleration.
Newton's Third Law
For every action there is an equal and opposite reaction
In space, there is almost no air, so there is virtually no friction. If an astronaut throws a ball in space with an initial velocity of 3.0 meters per second to the west, what will the ball's velocity be in a year? Assume there are no nearby planets.
3.0 meters per second to the west
A boy is running north with a beanbag in his hands. He passes a tree and at the moment he is beside the tree, he drops the beanbag. Will the beanbag land next to the tree? If not, will it be north or south of the tree?
Suppose the situation in question #4 is now changed. The boy is running, but now his friend stands beside the tree with the beanbag. As the boy passes, he barely taps the beanbag, causing it to fall out of his friend's hands. Will the beanbag land next to the tree? If not, will it be north or south of the tree?
next to the tree
A busy shopper is driving down the road. Many boxes lie piled on the back seat of the car - evidence of shopping activity. Suddenly, the shopper must hit the brakes to avoid a collision. Will the boxes be slammed farther back into the back seat, or will they slam into the front seat where the driver can feel them?
The boxes will slam into the front seat
When roads get wet, they can get slick. Obviously, then, the friction between a car's tires and the road decreases when the road is wet. Why?
The water fills in the grooves in the road, reducing how close the tire molecules can get to the road molecules.
In order to slide a refrigerator across the floor, a man must exert an enormous amount of force. Once it is moving, however, the man need not exert nearly as much force to keep it moving. Why?
Static frictional force is greater than kinetic frictional force
A child is pushing her toy across the room with a constant velocity to the east. If the static friction between this toy and the floor is 15 Newtons, while the kinetic friction is 10 Newtons, what force is the child exerting?
10 newtons east
In order to get a 15-kilogram object moving to the west, a force of more than 25 Newton's must be exerted. Once it is moving, however, a force of only 20 Newton's accelerates the object at 0.1 meters per second2 to the west. What is the force that static friction can exert on the object? What is the force of kinetic friction?
18.5 Newton's east
Static friction can exert a force of up to 700 Newton's in a 500-kilograms box of bricks. The kinetic frictional force is only 220 Newton's. How many Newton's of force must a worker exert to get the box moving? What force must the worker exert to accelerate the box at 0.1 meters per second2 to the south?
270 Newton's south
In order to shove a rock out of the way, a gardener gets it moving by exerting just slightly more than 100 Newtons of force. To keep it moving at a constant velocity eastward, however, the gardener needs only to exert a 45-Newton force to the east. What are the static and kinetic frictional forces between the rock and the ground?
45- Newtons to the west
Two men are trying to push a 710-kg rock. The first exerts a force of 156 Newtons east and the second exerts a force of 220 Newtons east. The rock accelerates at 0.20 meters per second2 to the east. What is the kinetic frictional force between the rock and the ground?
234 Newton's west
A child pushes against a large doghouse, trying to move it. The doghouse remains stubbornly unmoved. What exerts the equal and opposite force which Newton's Third Law of Motion says must happen in response to the child's push? What is that force exerted on?
The equal and opposite force is exerted by the doghouse on the child.
In a baseball game, a player catches a fast-moving ball. The ball stops in the player's hand. What evidence tells you that the player exerted a force on the ball? What exerts the equal and opposite force required by Newton's Third Law? What evidence does the player have for this force?
The player exerts a force on the ball because the ball's velocity changed. This means there was an acceleration, which means a force was exerted on the ball. The equal and opposite force is exerted by the ball on the player and is evidenced by the pain that the player feels when he catches the ball.
A man leans up against a wall with a force of 20 Newtons to the east. What is the force exerted by the wall on the man?
20 Newtons west