Introduction to Forces

Forces act upon an object by pushing or

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Two examples of noncontact forces are __________ and __________.

• friction

• gravity

• motion

• magnetism

Answer explanation

Gravity and magnetism occur without anything being touched directly.

Ex. a paperclip is pulled through air toward a magnet

Ex. a pen falls to the ground because of its attraction to Earth's gravitational pull

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Which of these are true statements about FORCE?

• The unit of force is the Newton.

• Contact forces include friction and gravity.

• Force is measured with a spring scale.

• A force is a push or a pull.

Think of 2 teams of students in PE playing tug-O-war. One of the teams is winning. What is true about the forces involved?

• The forces between the teams are balanced

• The forces between the teams are unbalanced

• There are no forces involved

• Both teams have equal net force

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Polly is pushing a box across the floor with a force of 30 N. The force of gravity is –8 N, and the normal force is 8 N. Which value could describe the force of friction if Polly could not move the box?

• –30 N

• –8 N

• 8 N

• 30 N

Answer explanation

The force of friction is resisting Polly's efforts. If the force of friction is to stop her, it must be the opposite of the force she is applying, and of equal or greater magnitude.

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15. Why is the Earth's gravity stronger than the Moon's gravity?

• The Earth is more massive than the Moon

• The Moon is so far away from Earth

• The Moon as no mass

• The Earth has a larger volume (takes up more space) than the Moon

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2. Which pair of objects has the largest gravitational force?

• A. marble and car

• B. marble and baseball

• C. car and bowling ball

• D. There is no gravitational force between any of these pairs of objects.

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What is the formula for force?

• F=M/A
• F=A/M
• F=M*A
• F=M*F

If net force acting on object is 0, then the force is considered to be..

• Balanced
• Unbalanced
• Equal in Direction
• Distance/Time

What is Newton's First Law known as? The Law of

• Friction
• Mass
• Inertia
• Gravity