Force and Motion

Felipe and Marsha were studying familiar forces and decided to do an investigation. They placed four equally sized blocks made of different materials on an elevated plastic tray. They watched as all of the blocks move down the tray. Which of the following forces prevents or slows down the blocks from moving down the tray?

• electric

• friction

• gravity

• magnetic

Answer explanation

Friction is the force that opposes the motion of the blocks as they move down the tray. It acts between the surfaces of the blocks and the tray, slowing them down, while gravity pulls them downward.

Tags

NGSS.3-PS2-1

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

• a sheet of glass

• a smooth wooden board

• a piece of construction paper

Answer explanation

The toy car will experience the most friction on a sandy beach due to the rough texture and loose particles of sand, which create more resistance compared to smoother surfaces like glass or wood.

The fifth-grade class is going on an outdoor education field trip. Each student is given a compass. What force causes the compass needle to point north?

• wind

• magnetism

• gravity

• electricity

Answer explanation

The compass needle points north due to magnetism. It is influenced by the Earth's magnetic field, which causes the needle to align itself with the magnetic north pole.

Tags

NGSS.3-PS2-3

Sadie rolls a marble down a ramp. When the marble reaches the bottom of the ramp, it then rolls across the floor. After a few seconds, the marble slows down, and then stops. What caused the marble to stop?

• The friction between the marble and the floor

• The air pressure pushing down on the marble.

• The force of gravity pulling the marble down.

• The magnetic attraction between the Earth and the marble.

Answer explanation

The marble stops due to the friction between the marble and the floor, which opposes its motion and gradually slows it down until it comes to a stop.

Tags

NGSS.MS-PS2-2

While riding home from soccer practice, Loreto realized that she was late for dinner. She knew that she needed to hurry in order to get home on time. What can Loreto do to increase her speed?

• increase the force applied to the bike pedals

• decrease the force applied to the bike pedals

• keep the force applied to the bike pedals the same

• Increase the amount of friction between her bike and the road

Answer explanation

To increase her speed, Loreto should increase the force applied to the bike pedals. This will generate more power, allowing her to ride faster and reach home on time.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

A baseball pitching machine is used by baseball players of all levels of experience to practice hitting. There is a dial on the machine that can change the speed of the pitch. Inexperienced players practice with slow pitches, and professionals practice with fast pitches. How does the pitching machine increase the speed of the baseball?

• The pitching machine adds more friction to the baseball to make them go faster.

• The pitching machine applies more force to the baseball to make them go faster.

• The pitching machine uses baseballs with more mass to make them go faster.

• The pitching machine applies less force to the baseball to make them go faster.

Answer explanation

The pitching machine increases the speed of the baseball by applying more force to it. This force propels the ball faster, allowing players to practice with varying pitch speeds.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

NGSS.MS-PS3-1

Zach, Beth, Randall, and Keisha are experimenting with forces. They each have a ball of the same mass and are going to move the balls on the same surface. The illustration shows their experimental setup.

The four students noticed that after the forces were applied, the balls rolled different distances. Which best explains why this happened?

• The balls experienced different amounts of friction.

• The balls did not all roll in the same direction.

• The balls were pushed with different amounts of force.

• The balls were not all pushed at the same time.                  

Answer explanation

The balls rolled different distances because they were pushed with different amounts of force. The greater the force applied, the further the ball would roll, explaining the variation in distances.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

In the game of golf, a player must move a ball several hundred yards to a hole. The player that can get the ball in the hole with the fewest amounts of hits, wins. When the golfer is close to the hole, they only need to putt the ball a few inches.

What kind of force should they apply to the golf ball?

• it does not matter because the ball will always move the same distance

• a large force

• a small force

• the golfer should add mass to the ball

Answer explanation

When putting the ball just a few inches from the hole, a small force is sufficient to gently roll the ball into the hole. A large force would overshoot, making a small force the correct choice.

Tags

NGSS.MS-PS2-2

Stefan pushes a cart with three books so it reaches the end of a track. Next, he puts six books onto the cart. Which claim explains what he must do so that the cart reaches the end of the track now that it has six books?

• use less force

• use more force

• use the same amount of force

• use a different cart

Answer explanation

Stefan must use more force to push the cart with six books because the increased weight requires additional force to overcome inertia and friction, ensuring the cart reaches the end of the track.

Tags

NGSS.MS-PS2-2

Lin-Yuan placed each of the objects on a smooth surface. He then used a spring device that applied 10 N of force to each object. Assume that the friction experienced by each object is the same.

Which object traveled farthest?

• metal washer

• rocks

• plastic disk

• wooden block

Answer explanation

The metal washer, being denser and more streamlined than the other objects, experiences less air resistance and rolls more easily. Thus, it travels the farthest when the same force is applied.

Tags

NGSS.MS-PS2-2