Force and motion

To determine motion, a _____ must be determined

• reference point

• location

• time

• speed

A change in motion is produced by _____.

• all forces

• balanced forces

• unbalanced forces

• the absence of force

When several forces act on an object, the forces combine to act as a _____________.

• opposing forces

• neutral force

• single force

• negative force

A student performs an investigation to study Newton’s second law: force = mass × acceleration. Two marbles of different masses are released at the top of a ramp and roll down the ramp. The student measures the distance each marble travels. The procedure is repeated three times and the average distance traveled by each marble is calculated. The data are shown in the table. Which of the following is the independent variable in the investigation?

• ramp height

• marble mass

• number of tests

• distance traveled by marble

Three toy boats with the same mass were in a lake. Two boats were moving and one was stopped. Each boat got bumped by another boat, but not in the same direction. All the boats changed speed as a result of being bumped. Use the information in the diagram to answer. Which toy boat(s) experienced the strongest force when it was bumped? How do you know?

• The blue toy boat experienced the strongest force because it takes a stronger force to slow something down than it takes to speed something up.

• The gray toy boat experienced the strongest force because it had the fastest ending speed.

• The orange and gray toy boats experienced the strongest forces because they both gained the same force as they sped up. The blue boat lost force, so it slowed down.

• All three toy boats experienced the same strength force because they changed speed by the same amount.

Three chairs were rolling across a flat office floor. The blue and red chairs are the same mass, and they have more mass than the yellow chair. Each chair was hit by another chair, but not from the same direction. Use the information in the diagram to answer.Which chair(s) experienced the strongest force when hit? How do you know?

• The blue and red chairs experienced the strongest force because they are both more massive than the yellow chair and they changed speed by the same amount.

• The red chair experienced the strongest force because it is as massive as the blue chair and has the highest ending speed.

• All three chairs experienced the same force because they changed speed by the same amount.

• The blue chair experienced the strongest force because it takes more force to slow an object than it takes to make it go faster.

Scott and James work at a grocery store. After the grocery store closed, they were playing a game with a shopping cart and Scott’s skateboard. They crashed the skateboard and the shopping cart two times. The shopping cart had more mass in Crash 2 than it did in Crash 1. Use the information in the diagram to answer. In which crash did the skateboard experience a stronger force? Why?

• The skateboard did not experience a force; only the shopping cart experienced a force in the crashes.

• Crash 2; the force on the cart was stronger in this crash, so the force on the skateboard was also stronger.

• The diagram doesn’t tell you anything about the force on the skateboard. It only gives information about the force on the shopping cart.

• The skateboard experienced the same force in both crashes. The shopping cart changed speed by the same amount in each crash, so the force on the skateboard was the same each time.

Sandra pushed a wooden block and it slid across the floor. The wooden block gradually slowed down and stopped after moving 10 meters. Why did the block stop moving?

• The floor exerted a force that is opposite to the direction of the block’s motion.

• The block ran out of force.

• The floor absorbs force from the block.

• All objects stop moving because their natural state is to be still.

Miniature golf is a game in which players hit a golf ball with a club, which causes the ball to roll along the flat ground. Three golf balls with the same mass were rolling on the ground. Each ball was hit by a golf club, but not from the same direction. All the golf balls changed speed as a result of being hit. Use the information in the diagram to answer. Which golf ball(s) experienced the strongest force when hit? How do you know?

• The white and purple golf balls because they gained force, while the green golf ball lost force.

• The green golf ball because it takes a stronger force to slow something down than to speed something up.

• The green golf ball because it changed speed the most.

• The white golf ball because it has the fastest ending speed.

At dinner, Hans passed the salt shaker to his sister Jessica by sliding it across the wooden table. The salt shaker gradually slowed down and stopped after moving 12 centimeters.Why did the salt shaker stop moving?

• The salt shaker ran out of force.

• The table exerts a force that is opposite to the salt shaker’s motion.

• The table absorbs force from the salt shaker.

• All objects stop moving because their natural state is to be still.