Unit 4 Forces

A push and a pull are two examples of which of the following?

• A force

• Velocity

• A law of motion

• A balanced force

Which term names a force of attraction between two objects, even if they are not touching?

• Inertia

• Gravity

• Friction

• Unbalanced force

Which of the following gives the definition of inertia?

• A sudden shift in acceleration

• A continuous downward force

• The tendency of objects to resist a change in motion

• The ability of objects to move in a smooth, curving path

Which of the following terms identifies a cause of change in motion?

• inertia

• mass and force

• balanced forces

• unbalanced forces

What term identifies a force that opposes motion and acts between two objects that are touching?

• inertia

• gravity

• friction

• balanced force

Four students used spring scales to measure the force needed to pull blocks made of different materials up a smooth ramp. All of the blocks moved at the same rate. The students recorded the force needed to move the different blocks: 6 N, 8 N, 7 N, and 5 N. Which of the following is a possible explanation for why the blocks require different amounts of force?

• The blocks all had different masses.

• The blocks all had the same mass but different sizes.

• The blocks had the same mass, but the force of gravity changed.

• Each student exerted the same force, but the friction was different.

Suri tapes batteries to three identical toy cars to give them different masses. Then, Suri measures how far each car rolls when she launches it from the same starting point using the same stretched rubber band. The three toy cars are pictured in the following illustration.

How will the force of the rubber band affect the cars?

• Car 3 will travel the longest distance.

• Car 1 will travel the shortest distance.

• Car 1 will be the least affected by the force acting upon it.

• Car 3 will be the least affected by the force acting upon it.

A spring scale measures force.

What is the force that causes the reading on the spring scale shown in the illustration?

• friction

• gravity

• mass

• weight

Two race cars with the same mass started moving on a race track at the same time. One car reached the finish line of the track in 15 sec, and the other reached the finish line in 20 sec. Why did the cars take different amounts of time to reach the finish line?

• The force of gravity slowed one car, but not the other car.

• The slower car did not experience any force, so it moved more slowly.

• The forces on one car were balanced and on the other car unbalanced.

• The engine of the faster car exerted more force than the engine of the other car.

Mindy wants to find out the average distance that each of six friends can throw a ball. She asks six friends of similar sizes and ages to throw a ball as far as possible from the same starting point. Mindy notices that one friend throws the ball much farther than the other five do. She wants her results to be accurate. What should Mindy do?

• Repeat the experiment for the person with the unusual result.

• Repeat the experiment using a different friend as a replacement.

• Repeat the experiment and ignore the results of the first experiment.

• Repeat the experiment two more times, and find averages for each of the six throwers.