When the net force is zero, forces are __________.
balanced
100
The measure of how much matter is in something is called _____________.
Mass
100
Name three forces that act without touching an object.
Gravity, magnetic force, electrostatic force
200
What two things does an arrow show us about force?
Direction and amount.
200
True or False: A car moving at a steady speed of 50mph has no forces acting on it.
False.
200
When forces on something are unbalanced, the motion of the object will change. Name the three changes in motion.
Acceleration (speeding up), deceleration (slowing down), change in direction
200
True or False: Only solid objects have mass.
False.
200
True or False: Gravity pulls, but never pushes.
True
300
Which of the forces listed below are contact forces?
friction, gravity, air resistance, magnetic force, electrostatic force
Friction and air resistance
300
True or False: More than one force can act on something at the same time.
True.
300
Which is true of a feather that is floating toward the ground at a steady speed?
A. the feather is decelerating
B. the net force on the feather is zero.
C. forces on the feather are unbalanced
D. gravity is the only force acting on the feather
B. the net force on the feather is zero
300
Which rock will speed up fastest?
A. a 1-pound rock acted on by a 1-pound force
B. a 1-pound rock acted on by a 2-pound force
C. a 2-pound rock acted on by a 1-pound force
D. a 2 pound rock acted on by a 2-pound force
B. a 1-pound rock acted on by a 2-pound force
300
Name the two forces that can attract or repel.
Magnetic force and electrostatic force
400
True or False: A force cannot move something without touching it.
False
400
What is the direction of the net force on water as it goes over a waterfall?
Down.
400
If you force a balloon under water and then let go, it will rise quickly to the surface. Which describes the force on the balloon just after it is let go?
A. the net force is zero
B. the force is unbalanced
C. the force arrows all point up
D. the force of gravity does not act on the balloon
B. the force is unbalanced
400
The Titanic was a very big ship that sank when it hit an iceberg. What was the main reason the captain of the Titanic couldn't stop the ship when he saw the iceberg?
A. the ship had a lot of mass
B. the ship had too much force
C. the ship was moving very fast
D. the ship was acted on by an unbalanced force
A. the ship had a lot of mass
400
Which pairs of electrostatic charges repel and which pairs of electrostatic charges attract?
Positive and Positive or Negative and Negative repel.
Positive and Negative attract.
500
What do we call the force that makes a car come to a stop when the driver pushes on the brakes?
Friction.
500
A large rock on top of a windy hill has four different forces acting on it, but it is not moving. What is the net force on the rock?
Zero.
500
When a skydiver jumps from an airplane, she begins to accelerate because the forces acting on her are unbalanced. The force of _____________ is greater than the force of ____________________.
The force of gravity is greater than the force of air resistance.
500
When things are pushed by a force, they speed up. Which things speed up the most?
A. things with the least mass that are pushed with the smallest force
B. things with the least mass that are pushed with the biggest force
C. things with the most mass that are pushed with the smallest force
D. things that the most mass that are pushed with the biggest force
B. things with the least mass that are pushed with the biggest force
500
Which magnetic poles repel? Which magnetic poles attract?
South pole and south pole or north pole and north pole repel.
North pole and south pole attract.