Review

A magnet must always have two poles, even if cut in half, because

• A magnet is made up of tiny magnetic domains that are aligned.

• Each pole divides in half and the magnetic field becomes weaker.

• Magnetic domains are out of alignment.

How can you increase the strength of an electromagnet?

• By moving the iron core to create friction.

• By adding more coils around the iron core.

• By decreasing the amount of current in the wire.

• By heating up the electromagnet.

An electromagnet differs from a permanent magnet because

• permanent magnets require an electrical current to produce a field.

• electromagnets can be turned off or weakened by reducing to stopping the flow of current.

• electromagnets only have one pole, while permanent magnets always have two.

• permanent magnets require the movement of electrons, while electromagnets do not.

This is a picture of a simple electromagnet. How can the electromagnet be made stronger?

• Add more coils of wire to the nail.
• Use a smaller battery.
• Reverse the poles of the magnet.
• Remove all the coils and the nail.

Why a ball falls to the ground?

• Earth's force of gravity is GREATER than the ball's, so the ball gets attracted to the ground. 
• Earth's force of gravity is LESS than the ball's, so the ball gets attracted to the ground. 

Which has more mass, Earth or the Moon?

• Earth
• Moon
• The same

Which has a STRONGER force of gravity, Earth or the Moon?

• Earth
• Moon

Why can astronauts jump and float a little on the Moon?

• Because the Moon's gravity is NOT that STRONG.
• Because the Moon's gravity is VERY STRONG. 

What law is best described by inertia?

• 1st
• 2nd
• 3rd
• law of conservation of mass

A person not paying attention while skateboarding hits a rock. The skateboard stops...they don't.

• The Law of Inertia (1st law)
• The Law of Acceleration (2nd law)
• The Law of Conservation of Momentum
• Action Reaction Law (3rd law)