Force and Motion Study Guide

Define Inertia:

A property of matter that describes the tendency of an object to resist changes in its state of motion.

Define Force:

A push or pull that acts on an object and may change its motion.

Debbie is an engineer who designs safety features to protect drivers in rear-end collisions. She has developed a new system that allows the front end of an auto mobile to bend or crumple during any head-on collision, thereby reducing the rate of deceleration experienced by the driver. The safety system is known as a front-end crumple zone. Suppose a rear-end automobile collision occurs between two cars. The orange car was waiting at a light with its breaks locked when the blue car collided with it from behind. The blue car had Debbie's front-end crumple zone system installed, which helped reduce part of the force of the collision. What is an additional safety feature that could have helped to reduce the force felt by the drivers of both cars even more?

A rear-end crumple zone installed in the orange car.

A car collides head on with a stationary sign. The collision brings the car to a stop, but the sign does not move. Which of the following design features would have reduced the force felt by both the car and the sign in the collision?

A sign that breaks loose from the ground when a force is applied to it.

Define Frame of Reference:

An object or point from which movement is determined.

Bryan and Alyssa are playing tug-of-war against Daniel and Maria. Bryan and Alyssa are exerting a combined force of 10 N. Daniel and Maria are exerting 12 N of force. Which of the following has resulted?

An unbalanced force moving everyone in Daniel and Maria's direction.

Trevor is pushing two boxes across a sidewalk. Box A has a mass of 4 kg. Box B has a mass of 8 kg. According to Newton's Second Law of Motion, if Trevor applies the same amount of force to each box, what will happen?

Box A will move further and faster that box B because it contains less mass.

An object's motion changes _______________.

Only when a nonzero net force is applied to the object.

Define Gravity:

The force of attraction that exists between any two objects that have mass.

Three dogs--Ed, Max, and Marcie--are pulling a dogsled along a patch of ice. Ed pulls with a force of 115 N; Max pulls with a force of 62 N; and Marcie pulls with a force of 90 N. If there are no forces pulling the sled backward, what is the net force acting on the sled?

267 N forward.

Define Friction:

A force that opposes motion.

An object that is moving will stop moving when which two factors occur?

Friction or Gravity

Mike and Joe take turns pitching a baseball, and Drew catches it. Mike can throw the ball harder than Joe can. Which of the following statements is true?

The ball travels faster when Mike throws it.

Define Unbalanced Force:

A force that has unequal magnitudes and/or directions.

A ball is dropped from a tower. From whose reference point is the ball approaching the observer?

A person standing on the ground beneath the tower.

Penny has two dogs named Fluffy and Butch. Penny also has two identical wagons. She puts one dog in each wagon and pushes each wagon with the same amount of force. The wagons travel in a straight line on level ground. Which of the following statements best compares the motion of the two wagons?

Fluffy's wagon will move faster.

The Voyager 1 spacecraft completed its space exploration mission in 1980 and has been traveling away from Earth at a speed of about 39,000 miles per hour. If no unbalanced forces act on Voyager 1, then what will happen?

It will continue traveling at the same speed.

Gina is driving her car down the street. She has a teddy bear sitting on the back seat. A dog runs in front of Gina's car, so she quickly applies the brakes. The force of the brakes causes the car to stop, but the teddy bear continues to move forward until it hits the car's dashboard. The teddy bear did not stop at the same time as the car because _________________.

Objects in motion tend to stay in motion unless acted upon by an out side force.

Isaac and Hailey set a wooden sailboat in a big puddle after a rainstorm. They sat on opposite sides of the boat, and on the count of three, they each began to blow as hard as they could on the sail of the boat. After a few seconds, the boat began to move toward Isaac. What happened?

The force Hailey's breath exerted on the boat was stronger than Isaac's.

An object has balanced forces acting on it. Which of the following describes the result these balanced forces have on an object?

The object will remain at rest.

A tire hanging from a tree is at rest . The force of gravity is pulling down on the tire. Another force, called tension, is pulling up on the tire. Tension is the pulling force that is transferred along the length of a string or rope. If the force of tension is equal to the force of gravity, then what will happen to the tire?

The tire will remain at rest.

In a football game, a defensive lineman exerts a force upon an offensive lineman, to be accelerate backward at 2 m/s2. If the offensive lineman's mass were doubled, how much force would the defensive lineman have to apply to accelerate the offensive lineman 2 m/s2 backward?

Twice as much.