Gravity and Inertia

What is gravitational force?

• the force of attraction between any two objects

• the force that makes inert objects start moving

• the only force that changes an object’s velocity

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Where is an object’s center of gravity?

• the part that is closest to the Earth

• the exact center of its mass

• all of the above

A paperclip and a computer are sitting on your desk. What is true about the gravitational force of these two objects?

• The computer attracts the paperclip with less gravitational force than the paperclip attracts the computer.

• There is no gravitational force between the paperclip and the computer.

• The computer and the paperclip attract each other with equal gravitational force.

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NGSS.MS-PS2-4

Why don’t we see the ground coming toward us?

• We have less mass than the Earth.

• We are already standing on the Earth.

• We have more inertia than the Earth.

​ (a)   is when two objects attract each other. ​ (b)   is when an object will stay in motion unless acted upon by another object or force. The planets of the solar system orbit around the Sun because of the Sun’s​ (c)   . Planets stay in their orbits around the sun because of the property of ​ (d)   . The planets would stay in a straight line because of ​ (e)   , but ​ gravity pulls on the planets and curves their paths into orbits around the Sun.

• gravity

• inertia

• magnetism

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​ (a)   a force which tries to pull two objects toward each other. ​ (b)   is when an object will stay in motion unless acted upon by another object or force. The planets of the solar system orbit around the Sun because of the Sun’s​ (c)   . Planets stay in their orbits around the sun because of the property of ​ (d)   . The planets would stay in a straight line because of ​ (e)   , but ​ gravity pulls on the planets and curves their paths into orbits around the Sun.

• gravity

• inertia

• magnetism

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NGSS.MS-ESS1-1

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NGSS.MS-PS2-4

During a demonstration of Newton's laws of motion, a student used the setup shown in Figure 1. The student flicked the index card with a fingertip, and the coin fell straight down into a plastic cup as shown in Figure 2. Which of these best explains why the coin fell straight down into the cup instead of remaining on the index card?

• The coin was at rest until the card was removed, so it tended to remain in the same location. Once the card was gone, the unbalanced force of gravity caused the coin to fall.

• Moving the card applied an action force on the coin. Since the card was gone, gravity applied a reaction force on the coin.

• The card had less mass than the coin, so a smaller force of gravity acted on the card. The larger force of gravity on the coin made it fall.

• The acceleration of the coin falling into the cup was equal and opposite to the acceleration of the card.

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NGSS.MS-PS2-1

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During a demonstration of Newton’s laws of motion, a student used the setup shown in Figure 1. The student flicked the index card with a fingertip, and the coin fell straight down into a plastic cup as shown in Figure 2. Which of these best explains why the coin fell straight down into the cup instead of remaining on the index card?

• The coin was at rest until the card was removed, so it tended to remain in the same location. Once the card was gone, the unbalanced force of gravity caused the coin to fall.

• Moving the card applied an action force on the coin. Since the card was gone, gravity applied a reaction force on the coin.

• The card had less mass than the coin, so a smaller force of gravity acted on the card. The larger force of gravity on the coin made it fall.

• The acceleration of the coin falling into the cup was equal and opposite to the acceleration of the card.

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NGSS.MS-PS2-1

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Why doesn’t the moon crash toward the Earth’s surface?

• It has more mass than the Earth, so it stays in one place while the Earth orbits it.

• It has a lot of mass, so it feels the Earth’s gravitational force less than smaller objects do.

• It is too small to fall through the Earth’s atmosphere and reach the Earth’s surface.

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NGSS.MS-ESS1-2

NGSS.MS-PS2-4

Why is it impossible to “defy gravity”?

• Nothing has enough force to resist gravity.

• You can’t defy gravity without going to another planet.

• Gravitational force exists every place where there are two objects.

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NGSS.MS-PS2-2

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