6th Grade Science – PMA Review 1

Which of the following is caused by a non-contact force?

• A magnet attracting a paperclip

• A person lifting a box

• Rubbing hands together to produce heat

• A car stopping due to brakes

Answer explanation

A magnet attracting a paperclip is an example of a non-contact force, as the magnet exerts a force on the paperclip without physical contact. The other options involve contact forces.

Tags

NGSS.MS-PS2-3

NGSS.MS-PS2-4

NGSS.MS-PS2-5

What happens to the gravitational force between two objects if the distance between them is doubled?

• The gravitational force becomes one-fourth as strong.

• The gravitational force doubles.

• The gravitational force stays the same.

• The gravitational force becomes twice as strong.

Answer explanation

According to Newton's law of universal gravitation, the force is inversely proportional to the square of the distance. If the distance is doubled, the force becomes one-fourth as strong.

Which force acts upward to support a cup placed on a desk?

• Gravity

• Friction

• Normal force

• Air resistance

Answer explanation

The normal force is the upward force exerted by the desk that supports the cup. It counteracts gravity, preventing the cup from falling through the desk.

A soccer ball is kicked across a field and eventually stops. Which force is mainly responsible for slowing the ball down?

• Gravity

• Friction

• Normal force

• Magnetic force

Answer explanation

Friction is the force that opposes the motion of the soccer ball as it rolls across the field. It acts between the ball and the ground, gradually slowing it down until it stops.

A ball is rolling on the ground and gradually slows down until it stops. Which two forces are primarily responsible for this change in motion?

• Friction and gravity

• Magnetism and gravity

• Air resistance and tension

• Normal force and buoyancy

Answer explanation

The ball slows down due to friction between the ball and the ground, which opposes its motion. Gravity also acts on the ball, keeping it on the ground. Thus, friction and gravity are the primary forces responsible for the change in motion.

Tags

NGSS.MS-PS2-2

Which of the following best describes normal force?

• A. A pulling force that acts through ropes or strings

• B. A pushing force that acts upward on objects resting on surfaces

• C. A resistive force that slows motion between surfaces

• D. A pulling force between two objects due to mass

Answer explanation

Normal force is the upward force exerted by a surface on an object resting on it, counteracting gravity. Thus, the best description is B: a pushing force that acts upward on objects resting on surfaces.

Tags

NGSS.MS-PS2-2

If the distance between Earth and the Moon increased, what would happen to the gravitational force between them?

• It would increase.

• It would decrease.

• It would stay the same.

• It would disappear completely.

Answer explanation

The gravitational force between two objects decreases as the distance between them increases, according to Newton's law of universal gravitation. Therefore, if the distance between Earth and the Moon increased, the gravitational force would decrease.

Tags

NGSS.MS-ESS1-2

NGSS.MS-PS2-4

A book is resting on a desk. Which force is acting upward on the book, preventing it from falling through the desk?

• Gravity

• Normal force

• Friction

Answer explanation

The normal force is the upward force exerted by the desk on the book, counteracting gravity. This force prevents the book from falling through the desk, making it the correct answer.

If two people move farther apart from each other, what happens to the gravitational force between them?

• The force decreases

• The force increases

• The force stays the same

• The force becomes zero

Answer explanation

According to Newton's law of universal gravitation, the gravitational force decreases as the distance between two objects increases. Therefore, as two people move farther apart, the gravitational force between them decreases.

Which of the following actions involves a contact force?

• A. The wind blowing leaves off a tree

• B. The Sun keeping planets in orbit

• C. A person kicking a soccer ball

• D. A balloon repelling another balloon

Answer explanation

C is correct because kicking a soccer ball involves direct contact between the foot and the ball, making it a contact force. The other options involve non-contact forces like gravity or air pressure.