Science Unit 1 Test 8th Grade

What is a force?

A push or pull that can change an object's motion.

When do forces cause an object to change its motion?

When the forces are unbalanced and the net force is greater than zero.

What is net force?

The total force acting on an object after all forces are combined.

What does it mean if forces are balanced?

The net force is zero.

What happens to an object at rest when forces are balanced?

It remains at rest.

What happens to a moving object when forces are balanced?

It continues moving at a constant velocity.

What does constant velocity mean?

The object does not speed up, slow down, or change direction.

What is Newton's 1st Law?

An object remains at rest or continues moving at constant velocity unless an unbalanced force acts on it.

What is another name for Newton's 1st Law?

The Law of Inertia.

What is inertia?

The resistance of an object to a change in its motion.

How does mass affect inertia?

Objects with more mass have more inertia.

What is friction?

A force that opposes motion.

Which direction does friction act?

Opposite the direction of motion.

What must be overcome to slide an object across a floor?

The friction between the object and the floor must be overcome by an applied force.

What determines the gravitational pull between two objects?

The masses of the objects and the distance between them.

How does increasing mass affect gravitational pull?

Increasing mass increases gravitational pull.

How does increasing distance affect gravitational pull?

Increasing distance decreases gravitational pull.

What is the relationship between mass and gravity?

Anything with mass exerts a gravitational pull.

What is mass?

The amount of matter in an object.

What is the unit for mass?

Kilograms (kg).

Does mass depend on gravity?

No. Mass stays the same even when gravity changes.

What is weight?

The force of gravity acting on an object.

What is the unit for weight?

Newtons (N).

Does weight depend on gravity?

Yes. Weight changes when the gravitational force changes.

How do you calculate weight?

Weight = mass × gravitational acceleration, or W = mg.

What is Earth's gravitational acceleration?

9.8 m/s².

How do you convert pounds to kilograms?

Divide the mass in pounds by 2.2.

What is terminal velocity?

The point during a fall when air resistance equals gravity and the object falls at a constant velocity.

What happens to the net force at terminal velocity?

The net force is zero.

What is Newton's 2nd Law?

An object's acceleration depends on the net force acting on it and its mass.

What is the formula for force?

F = ma.

What is the formula for acceleration using force and mass?

a = F/m.

What happens to acceleration when force increases and mass stays constant?

Acceleration increases.

What happens to acceleration when mass increases and force stays constant?

Acceleration decreases.

What is Newton's 3rd Law?

For every force, there is an equal and opposite force.

Why can two objects have equal and opposite forces but different accelerations?

The objects can have different masses, and the object with less mass accelerates more.

What is the formula for acceleration using velocity and time?

a = (Vf - Vi) / t.

What is average speed and its formula?

Average speed is distance divided by time: S = d/t.