Force and Motion: Friction, Gravity, and Mass

How can friction, gravity, or a change in mass affect motion?

​PS.5.2.1 Carry out investigations to explain how factors such as gravity, friction, and change in mass affect the motion of objects.

• how friction affects motion.

• the role of gravity in motion.

• how mass influences motion.

​This week we have investigated...

Motion is the change in position of an object.

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What is motion?

Friction

Friction is a force that opposes motion between two surfaces in contact.

Multiple Choice

What do you think happens when you push a toy car on different surfaces?

• It moves faster on carpet.

• It moves slower on carpet.

Friction in Action

Friction depends on the types of surfaces and how hard they are pressed together.

What do you think about these surfaces?

Multiple Choice

Which surface do you think has the most friction?

• Ice

• Sandpaper

Multiple Choice

A wagon is pushed in a straight line. How would an increase in friction on the wagon wheels affect the wagon?

• It would cause the wagon to move faster.

• It would cause the wagon to change mass.

• It would cause the wagon to change direction.

• It would cause the wagon to slow down.

Gravity is the force that pulls objects toward each other.

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Multiple Choice

What happens to a ball when you drop it?

• It floats away.

• It falls to the ground.

Multiple Choice

A boy throws a baseball up in the air. Why does the baseball fall back down to the ground?

• the mass of the baseball decreases, causing it to fall

• the weight of the ball causes the ball to fall

• the force of gravity causes the ball to fall

• the density of the ball causes the ball to fall

Mass is the amount of matter in an object.

Multiple Choice

If you have two toy cars, one heavy and one light, which one do you think will go further when pushed?

• heavy car

• light car

A change in mass can affect how much force is needed to move an object.


Look at these examples:
Which cart needs more force to move?
What about the wagons?

Poll

TRUE of FALSE:

More mass means more force is needed to move an object.

• TRUE

• FALSE

Poll

TRUE or FALSE:

Less mass means less force is needed to move an object.

• TRUE

• FALSE

Multiple Choice

If two boxes are pushed with the same amount of total force, and one weighs 1kg and the other weighs 100kg, which one will accelerate faster?

• 1kg box

• 100 kg box

• they will accelerate at the same rate

Multiple Choice

Students described the amount of force needed to change the motion for each ball from idle to rolling.  Which statement is true?*

• The beach ball has less mass, but it took more force to make it roll.
• The bowling ball has less mass, but it took more force to make it roll.
• The beach ball has more mass, therefore it took less force to make it roll.
• The bowling ball has more mass, therefore, it took more force to make it roll.

3 Big Ideas...

• Friction slows down motion.

• Gravity pulls objects down.

• More mass = more force to move. Less mass = less force to move.