8th Grade - Chapter 2, Section 3 ~ Newton's First and Second Laws

An object in motion will stay in motion until a force acts to change its A or B.

A: Speed B: Direction

If a 4000 N force acts on an 800 kg car, what is the acceleration of the car?

Acceleration = Net Force / Mass Acceleration = 4000 N / 800 kg Acceleration = 4000 kg X m/s2 / 800 kg Acceleration = 5 m/s

Who was Isaac Newton?

An English scientist in the 1600s who proposed the 3 basic laws of motion.

Who was Galileo Galilee?

An Italian astronomer

What is Newton's First Law of Motion?

An object at rest will remain at rest and an object moving at a constant velocity will remain moving at a constant velocity, unless acted on by an unbalanced force.

What are two ways to decrease the acceleration of an object?

Decrease the force or increase the mass

How could you keep an object's acceleration the same if the force acting on the object were doubled?

Double the mass

What is the equation for Newton's second law of motion, if solving for force?

Force = mass X acceleration

On Earth what two unbalanced forces often change an object's motion?

Friction and Gravity

What are two ways to increase the acceleration of an object?

Increase the force or decrease the mass

Explain why you feel pressed back into the seat of a car when it accelerates.

Inertia pushes you back because it resists the change in motion. You're at rest, and your body wants to remain at rest, so when the car accelerates, you don't move until the seat of the car pushes you forward.

What is another name for Newton's first law?

Law of Inertia

Acceleration is measured in what unit?

Meters per second per second ~ m/s2

What is the short form for his unit of force?

N ~ newtons

Calculate the force needed to accelerate a 25 kg create at a rate of 3 m/s2.

Net Force = Acceleration X Mass Net Force = 2 m/s2 X 25 kg Net Force = 75 m/s2

What is the equation for the relationship of acceleration, net force, and mass?

Net force (F) Acceleration (a) = ________________ Mass (m)

What did Galileo suggest?

Once an object is in motion, there is no force needed to keep it in motion.

What is Newton's Second Law of Motion?

The acceleration of an object depends on the object's mass and the net force acting on it.

What is one Newton?

The force required to give a 1 kg mass and acceleration of 1 m/s2.

What is the relationship between inertia and force?

The greater the inertia, the greater the force needed to change its motion.

What is the relationship between mass and inertia?

The greater the mass of an object the greater its inertia.

Which object has a greater inertia: an empty wheelbarrow or one filled with wood?

The one with wood - greater mass

How does Newton's first law explain what happens to passengers when a car stops quickly?

The passengers move forward in their seat because of inertia. They keep moving until acted upon by the unbalanced force of the seat belt.

What is inertia?

The tendency of an object to resist a change in motion.

According to Newton's second law, in what unit is force measured?

kg times meters per second per second (kg X m/s2)

Mass is measured in what unit?

kilograms ~ kg