Gravitational Forces
True or False: Gravity is ALWAYS a push, NEVER a pull
False
True or False: Magnetic force is ALWAYS a pull, never a push
False
Electric Force lines go out of a ___________ charge.
Positive
How are force fields unique from other forces?
They do not require the objects to be touching in order to act on them (non-contact forces).
What is the only significant force acting on a projectile?
Gravity
If you go to the moon, your _______ would change, but your _______ would stay the same.
If you go to the moon, your weight would change, but your mass would stay the same.
What 2 factors affect the strength of a magnetic force?
1) The arrangement of particles in the object
2) The distance between objects
What 2 factors affect the strength of an electric force?
1) The charge of an object
2) The distance between objects
"Opposites attract" and "similar repel" help us describe interactions in which types of force fields?
Magnetic fields (North vs. South) and Electric fields (Positive vs. Negative)
What 2 factors affect the strength of a gravitational force?
1) The mass of the objects
2) The distance between objects
What is the law of Universal Gravitation?
All objects that have mass attract all other objects that have mass.
Which poles of a magnet attract each other? Which poles repel each other?
North and South attract each other
North repels North and South repels South
Which electric charges attract each other? Which charges repel each other?
Positive and Negative attract each other.
Positive repels Positive and Negative repels Negative.
Gravitational Forces, Magnetic Forces, and Electric Forces all have one common factor (they depend on the same thing). What is it? How does it affect each of them?
They all depend on distance. Each of these forces decrease in strength as the distance between objects increases.
In our model of gravity, why did the marble move toward the golf ball? What happened when we moved the marble farther away?
The marble rolled toward the golf ball because the golf ball has more mass, giving it more gravity. When the marble was farther away, it didn't roll toward the golf ball because the greater distance makes gravity weaker.
What has more gravity, the Earth or the Sun? Why?
Why are we pulled toward the Earth and not the Sun?
The Sun has more gravity because it has more mass.
We fall toward the Earth because we are much closer to the Earth than the Sun, so the Sun's gravity does not affect us as strongly.
Which direction do magnetic field lines radiate from the poles of a magnet?
How do the interactions of field lines between 2 magnets determine a push or pull?
Field lines radiate out of a North pole and into a South pole.
If the lines connect the magnets, they will attract. If they interfere/collide with each other, they will repel.
What causes an object to have a positive charge? What causes an object to have a negative charge?
An object will be positive if it has more protons than electrons.
An object will be negative if it has more electrons than protons.
How are magnetic and gravitational forces similar? How are they different?
Similar: Both are non-contact, both can pull, both decrease in strength as distance increases
Different: Caused by different properties (arrangement of particles vs. mass), gravity affects all objects while magnetism only affects certain objects, gravity can only pull while magnets can both push and pull
DAILY DOUBLE
Pick any question worth 300 or fewer points - it is now worth double
If the Earth's gravity is pulling the moon, why doesn't the moon crash into the Earth?
Draw a picture of the motion of the moon relative to earth. Your picture needs to include...
a) An arrow representing the inertia/current motion of the moon
b) An arrow representing the gravity of the Earth
c) An arrow/line representing the actual path that the moon will travel
The moon is moving just fast enough (to the side) to fall around the Earth.
(See picture)
Draw a picture of 2 magnets that have their North poles facing each other. Include the magnetic field lines of each magnet and how they are interacting. Are they pulling together or pushing apart? How can you tell?
(See picture)
Pushing apart, the field lines do not connect the magnets.
Look at the picture. What charge does each of the objects have? How do you know? Are the objects pulling together or pushing apart? How do you know?
They both have a negative charge. You can tell because the electric field lines are radiating into both of them. They are pushing apart because the field lines do not connect them.
How are magnetic and electric forces similar? How are they different? (List 2 for each)
Similar: Both are non-contact, both can push or pull, both have field lines that arrange in a similar pattern, both decrease in strength as distance increases, opposites attract and similar repel (charges and poles)
Different: Caused by different properties (arrangement of particles vs. charge), affect different objects (metals/magnets vs. charged objects), magnets always have 2 poles whereas charges can exist on their own
If force fields are invisible, how do we know they exist? How can we map their size/shape? Give an example that we used in class.
We know they exist because of their effect on objects that we can see.
We can map their size and shape by using a test object.
(Various Examples)