Physics Newton first law

The astronomer Copernicus publicly stated in the 1500s that Earth

• does not move.
• revolves around the sun.
• is slowing down.
• moves in a straight line.

Galileo found that a ball rolling down one inclined plane would roll how far up another inclined plane?

• The ball would not roll up the other plane at all.
• To nearly its original height
• To about one quarter its original height
• To nearly twice its original height

Friction is a force that always acts

• perpendicular to an object's motion.
• opposite to an object's motion.
• in the same direction as an object's motion.

The law of inertia states that an object

• will continue moving at the same velocity unless an outside force acts on it.
• will continue moving in a straight line unless an outside force acts on it.
• at rest will remain at rest unless acted on by an outside force.
• will do all of the above.

The law of inertia applies to

• objects at rest.
• moving objects.
• both moving and nonmoving objects.

After a cannonball is fired into frictionless space, the amount of force needed to keep it going equals

• zero, since no force is necessary to keep it moving.
• twice the force with which it was fired.
• one half the force with which it was fired.
• the same amount of force with which it was fired.

If the force of gravity suddenly stopped acting on the planets, they would

• spiral slowly towards the sun.
• continue to orbit the sun.
• move in straight lines tangent to their orbits.
• spiral slowly away from the sun.

A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. The reason this can be done is that

• gravity pulls very hard on the milk carton.
• the milk carton has very little weight.
• the milk carton has inertia.

The force required to maintain an object at a constant speed in free space is equal to

• the mass of the object.
• the weight of the object.
• zero.
• the force required to stop it.

An object following a straight-line path at constant speed

• has no forces acting on it.
• has a net force acting on it in the direction of motion.
• has zero acceleration.
• must be moving in a vacuum.