Noncontact Forces

Noncontact Forces

Noncontact Forces

• Forces that act from a distance

• The objects to not have to touch each other

• Electrical Force, Magnetic Force, Gravitational Force

• Measured in Newtons

Multiple Choice

Why are some forces considered to be noncontact forces?

• Objects must be far apart in order to exert a force

• Objects do not have to touch each other to experience a force

• Objects push each other apart to increase the distance between them.

• Objects must be large in size in order to exert a force that is strong enough to notice.

Multiple Choice

All of these are noncontact forces, except

• electricity

• friction

• gravity

• magnetism

Electrical Forces

• Is a push or pull between charged objects

• Static electricity is a buildup of electrical charge on an object

• Objects can have a positive or negative charge depending on their number of electrons (more electrons than protons=negative charge)

• Like magnets, same or like charged objects repel, while opposite charged objects attract.

Electrons "jump" from your finger to the doorknob.

Multiple Choice

What happens when you touch a metal doorknob after rubbing your shoes on the carpet?

• The doorknob sends a burst of electric current into your body

• Electrons go from your finger into the doorknob

• The doorknob sends millions of electrons into your finger

• Your finger becomes negatively charged

Multiple Choice

Electrical charge built up on the surface of an object is called _________________.

• static electricity
• current electricity
• lightning
• electrons

Magnetic Forces

• Occurs between two magnets or between a magnet and iron, steel, nickel, or cobalt.

• Magnets have two poles, north and south, where the forces are the strongest.

• Opposite poles attract, or pull, on each other.

• Like poles repel, or push away from, each other.

• All magnets have an invisible magnetic field: the area around a magnet where its force acts. It is strongest around the poles.

• The strength of magnetic forces depend on distance and materials.

Multiple Choice

What are two factors that affect the strength of magnetic forces?

• poles and gravity

• distance and direction

• distance and material

• electricity and gravity

Multiple Choice

A magnetic field of a magnet gets_____________the further magnetic object moves away from the magnet

• Positive

• Negative

• Stronger

• Weaker

Multiple Choice

Where is the force of attraction the strongest on a magnet?

• at the poles
• in the middle
• above the magnet
• below the magnet

Multiple Choice

A magnet will pick up a nail, but not a penny because the nail

• has rust on it.
• is lighter than the penny.
• has a sharp point.
• contains iron.

Gravitational Force

• A force that pulls all objects toward each other.

• Gravitational force depends on two factors, mass and distance.

• The more mass an object has, the stronger its gravitational force.

• The greater the distance between two objects, the less gravitational force they exert on each other.

• 
  

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Multiple Choice

Melanie watched the path a baseball followed after a pitcher threw it. She noticed that the ball traveled horizontally away from the pitcher as well as downward toward the ground. What force caused the ball to accelerate in the downward direction when it was thrown?

• applied force

• air resistance

• gravitational

• electrical

Multiple Choice

What two factors determine the strength of the gravitational force between two objects?

• acceleration and distance

• speed and distance

• mass and distance

• mass and speed

Multiple Choice

At which position will the astronaut feel a greater gravitational pull?

• Position B

• Position A

• Both will feel the same amount of gravitational pull

• Both are in zero gravity

Multiple Choice

When the mass increases, the strength of the gravitational field _______.

• increases

• decreases

• remains the same

• become negatively charged