PART 2: Forces and Motion Universal Forces

Forces & Motion REVIEW

TARGET 3: Identify and describe the forces that attract and repel all object in the
universe.

TARGET 4: Explain what law of universal gravitation is.

PART 2: Universal Gravitation 1

Universal Forces

Electric force and magnetic force are the only
forces that can both ATTRACT and REPEL.

Electric forces act between charged objects or
particles such as electrons and protons.

Objects with the SAME charge (+ and +) or (- and -) will repel each other

Objects with an opposite charge will attract each other (+ and -)

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Multiple Select

Which are the only two forces that can both attract and repel?

• electric force

• atmospheric force

• magnetic force

• total force

Multiple Select

Which of the following combinations will REPEL?

Select all that apply

• +/+

• +/-

• -/-

Multiple Select

Which of the following combinations will ATTRACT?

Select all that apply

• +/+

• +/-

• -/-

Magnetic Forces

Magnetic forces act on certain metals, on the poles of magnets, and on moving
charges.

●Magnets have two poles, a south and a north

●Opposite poles attract while like poles repel

3

Open Ended

What are the two poles that magnets have called?

Nuclear Forces

A nuclear force is a strong attractive force between nucleons in the atomic
nucleus of an atom that holds the nucleus together.

●The strong nuclear force overcomes the electric force of repulsion that
acts among the protons in the nucleus.

●The weak nuclear force is involved in certain types of radioactive
processes and is weaker than the strong nuclear force.

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Multiple Choice

What do nuclear forces do (on the atomic level)?

• holds the nucleus together

• is why the nucleus of an atom is round

• it has no effect on the nucleus, just the electrons are affected

• none of the answers are correct

Gravitational Forces

Gravitational forces are an attractive force that acts between any two
masses.

●Newton’s law of universal gravitation states that every object in the
universe attracts every other object.

5

Multiple Choice

Newton's __ states that every object in the universe attracts every other object.

• first law of motion

• second law of motion

• universal gravitation

• third law of motion

Gravitational Forces

Gravity acts over large distances.

●The gravitational force of two objects depends on their masses and the
distance between them.

●Greater mass equals greater gravitational force while greater distances
between them result in a decreased gravitational force.

●Gravity is the weakest universal force but is the most effective over long
distances.

6

Multiple Choice

Greater mass equals ___ force.

• greater

• decreased

• opposite

• the same

Multiple Choice

Greater distance equals ___ force.

• greater

• decreased

• opposite

• the same

Multiple Choice

Which of the following is the WEAKEST of the universal forces?

• strong nuclear force

• weak nuclear force

• gravity

• none of the answers are correct

Multiple Choice

Which of the following is most effective over long distances?

• strong nuclear force

• weak nuclear force

• gravity

• none of the answers are correct

The Earth, Moon, and Tides

●Earth’s gravitational forces keeps the moon in an elliptical orbit around
Earth.

●A centripetal force is a center-directed that continuously changes the
direction of an object to make it move around the center.

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The Earth, Moon, and Tides

Gravitational pull of the Moon produces two bulges in Earth’s oceans. These
bulges are what created Earth’s tides.

One bulge is on the side of the Earth closest to the Moon, the other is on the
side farthest from the Moon.

Earth’s rotation results in two high and
two low tides per day

8

Satellites in Orbit

Satellites are artificial objects that are placed in orbit around a space-bound
object (Earth or Moon in our solar system).

Most are used for communication as well as making observations of the
objects in the solar system.

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