Picking up a heavy box is much more difficult than putting it down. What is a

likely explanation for this?

• Pushing force is more difficult to accomplish than pulling force.

• The force of gravity acts against you when you try to push something to the

  ground.

• The action is less difficult because nothing is pulling the object toward the

  ground.

• The force of gravity is pulling the box toward the ground which makes the

  action of putting the box down easier to do.

Some students were investigating which surfaces would allow a ball to roll the farthest. Which of the following

would be essential in their investigation?

• Stopwatch, meter stick, calculator, soccer ball, 41⁄2-foot–tall student

• Grassy field, gym floor, concrete sidewalk, soccer ball, meter stick

• Soccer ball, bowling ball, beach ball, stopwatch, meter stick

• 4-foot-tall student, 41⁄2-foot-tall student, 5-foot-tall student, soccer ball, meter stick

This experiment can be used to determine —

• how mass affects the force needed to move objects

• how force affects the mass of two objects

• how the force used to pull a dictionary affects the mass of a box of marbles

• how the mass of a box of marbles affects the mass of a dictionary

A push or pull that acts on an object

• force

• motion

• pull

The movement an object has when acted on by a force

• motion

• gravity

• friction

• balanced force

When an object is moved toward the source of the force

• push

• pull

• friction

When an object is moved away from the source of the force

• friction

• motion

• push

• pull

A force that pulls objects toward Earth's center

• push

• friction

• gravity

• pull

A force that resists and slows down the motion of an object

• push

• motion

• friction

• pull

Which procedure should students include in their design?

• Conduct five trials, using a different scale to pull each block of wood

• Conduct five trials, pulling a different side of each block each time

• Conduct five trials, using a different table for each trial

• Conduct five trials, pulling each block of wood in the same way for each trial