Force and Motion

Brian and Emily are testing different paper airplane designs to see which will allow a plane to go the farthest. Emily folds her plane and attaches a paperclip to the front of it. After she throws the plane, it travels about fifty feet and then starts to fall to the ground.  
 Why does the plane eventually fall to the ground?

• The force of air resistance stops acting on the plane
• The plane was not designed to carry a load like the paperclip
• The force of gravity is greater than the forces keeping the plane in the air
• The paperclip creates a magnetic force that attracts the plane to the ground.

Aaron is playing with a soccer ball at the top of a hill. Aaron kicks the ball and it rolls down the hill. Which of the following best describes what happens as the ball rolls?

• The force of gravity pulls the ball downhill
• The force of friction causes the ball to roll faster down the hill
• The force of gravity is balanced by air resistance acting on the ball
• The force of friction is greater than the force of gravity acting on the ball

While Carmen is at the park with her family, she walks up to a wishing well. She throws a penny down the well, and she hears a splash at the bottom. Which of the following best describes what happens as the penny falls?

• The force of gravity is equal to the air resistance acting on the penny
• The magnetic force of the well attracts the penny and causes it to fall even faster
•   The force of friction acts against air resistance, causing the penny to fall even faster
• The force of air resistance acts against gravity, but it is not enough to overcome gravity

Which of the following explains why a parachute makes a person falling from a great height fall more slowly?

• The parachute reduces the friction in the air
• The parachute pulls upward, so the fall is slower.
• The parachute causes air resistance, which slows the fall
• The parachute decreases the pull of gravity on the person wearing it

Gravity gets weaker as you travel farther from the surface of Earth. Which of the following examples correctly illustrates this idea?

• Satellites that orbit Earth will always fall back to Earth eventually.
• Astronauts can float because Earth's gravity is not as strong in orbit.
• Airplanes can fly because there is much less gravity high in the sky.
• here is no gravity on the Moon because it is too far away from Earth.

Magnets have a negative and positive pole. What happens if you try to touch the positive ends of two magnets together?

• The positive poles will repel each other because opposite poles attract
• The positive poles will be attracted to each other because matching poles attract
• The positive poles will neither attract nor repel each other
• The positive poles will create gravity and attract other objects

A toy car rolling along different surfaces will experience different amounts of friction. The toy car would encounter the most friction when rolling on which of the following surfaces?

• a sandy beach because the rougher surface the more friction
• a sheet of glass because the smoother the surface the more friction
• a smooth wooden board because it creates heat
• a piece of construciton papar because it can be torn into pieces

Magnets have a negative and positive pole. What happens if you try to touch the positive pole of one magnet to the negative pole of another magnet?

• The negative and positive poles will repel each other.
• The negative and positive poles will cancel each other out
• The negative and positive poles will be attracted to each other
• The negative and positive poles will neither attract nor repel each other

David and Peter were moving a bookshelf across the carpet in their classroom. Even though they pushed as hard as they could, the bookshelf would only move a few inches at a time.  
Which of the following best explains what happened as they tried to push the bookshelf?

• The force of gravity opposed the motion of the bookshelf
• The force of friction opposed the motion of the bookshelf
• When they tried to push the bookshelf, air resistance acted against them
• When they pushed the bookshelf, the bookshelf pushed back with an equal and opposite force

Philip is playing tug of war with Nancy. They both understand that to win the game of tug of war, one player must pull the flag over their opponent's line, but during this particular game, the flag tied to the center of the rope is not moving.  
What is happening to the rope in this example?

• Philip is applying more force in one direction
• Nancy is applying more force in one direction
• Philip and Nancy are applying equal forces in the same direction
• Philip and Nancy are applying equal forces in opposite directions