Unit 7- Lessons 1 and 2

Which of the following is considered a contact force?

• The force between two magnets.

• The friction between an object and air.

• The gravitational pull of a planet.

• The force between two charged particles.

A student is brushing her hair. As the hairbrush is brought near her head, the hair seems to reach toward the hairbrush. Which of the following is the BEST explanation?

• Two gravitational fields are interacting.

• Two magnetic fields are interacting.

• Two electric fields are interacting.

• Two electromagnetic fields are interacting.

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Below is an image of a magnetic field.

Where is the magnetic field the strongest?

• A

• B

• C

• D

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Which phenomenon is most directly responsible for Earth's magnetic field?

• The moon's gravitational pull on Earth.

• Earth's rotation about its axis.

• The moon's revolution around Earth.

• Earth's revolution around the sun.

An index card is placed on the top of a drinking glass. A coin is then placed on top of the index card. A student quickly flicks the card sideways off the glass. Which of the following explains why the coin falls into the glass rather than moving to the side with the index card?

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

• Newton's law of universal gravitation

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In order for a space shuttle to leave Earth, it must produce a great amount of thrust. Its rocket boosters create this thrusting force by burning great amounts of fuel. However, once in space, the shuttle needs very little fuel. It circles Earth while gravity pulls it toward Earth. What term describes the motion of the shuttle around Earth?

• orbit

• gravity

• interia

• weight

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A box of books is on the floor. The following picture shows a push and a pull acting on the box.

What is the net force toward the right on the box?

• 0 N

• 50 N

• 100 N

• 2500 N

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NGSS.MS-PS2-2

High and low tides are the regular pattern of rising and sinking ocean-water levels. They are formed as a result of the gravitational forces of the moon and sun on Earth’s oceans. The moon has a greater effect on Earth’s oceans than the sun. Why would the moon have a greater effect than the sun?

• The moon is closer to Earth than the sun is.

• The moon is not as hot as the sun.

• The moon has less mass than Earth.

• The moon has less mass than the sun.

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What is true of an object that is in free fall?

• The forces of thrust and gravity balance one another.

• No forces are acting on it.

• The forces of air resistance and gravity balance one another.

• Only the force of gravity is accelerating it.

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Jessica is comparing two different balls. One ball has a mass of 1 kg. The other ball has a mass of 2 kg. She pushes each with a force of 100 N. How does the acceleration of the two balls compare?

• The 1-kg ball accelerates the same as the 2-kg ball.

• The 1-kg ball accelerates the same as the 2-kg ball.

• The 1-kg ball accelerates four times as much as the 2-kg ball.

• The 1-kg ball accelerates twice as much as the 2-kg ball.

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