Forces A Review

The force that always acts opposite to the direction of motion Friction

It would be easiest ride your bike across A: gravel B: sand C: the grass D: a side walk

Buoyancy is the upward force created by liquids Archimedes principle: the buoyant force is equal to weight of the water displaced.

The cube has force of gravity 10 Newtons acting on it The cube has force of gravity 10 Newtons acting on it. What is the Buoyant force? A: 10 Newtons B: more than 10 Newtons C: less than 10 Newtons D: not enough information

Gravity Pulls objects with mass together More mass=more gravity Closer together=more gravity

Hector weighs 60 kg on Earth what is his weight if he went to the moon?

The gravitational force between each planet and the Sun is A: the same because it is only affected by the gravity of the Sun B: larger for planets farther from the Sun because more force is needed to keep them in orbit C: determined by the mass of the Sun, the mass of the planet, and the planet’s distance from the Sun.

Newton’s First Law of Motion Part 1: An object at rest remains at rest unless acted on by an unbalanced force

Newton’s First Law of Motion Part 2: An object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force

The more mass an object has the more inertia it has. True or False

Newton’s Second Law of Motion The acceleration of an object depends on the mass of the object and the amount of force applied Part 1: Acceleration depends on mass Part 2: Acceleration depends on force

What happens when the force increases? The stronger the force on an object, the greater its acceleration.

What happens if the mass is increased? There must be more force to keep the same acceleration 5 N 8 N

Newton’s Third Law of Motion Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

Forces act in pairs Action force=the force that does the first action Reaction force=the force that occurs as a response to the action force Action: the exhaust pushes down Reaction: the rocket moves up

According to Newton’s 3rd law, forces always act in _______ pairs A: equal but opposite B: unequal but opposite C: equal but complementary

1. Stepping on a wagon and watching it move away from you Name that law 1. Stepping on a wagon and watching it move away from you 3rd

2. If a driver turns a corner too quickly your body leans sideways Name that law 2. If a driver turns a corner too quickly your body leans sideways 1st

3. Explains the relationship between force, mass and acceleration Name that law 3. Explains the relationship between force, mass and acceleration 2nd

Name that law 4. When you walk, you push on the sidewalk, and the side walk pushes on you with equal force 3rd

5. A bowling ball knocks down a set of pins and keeps rolling Name that Law 5. A bowling ball knocks down a set of pins and keeps rolling 1st

Name that Law 6. A soldier shoots a rifle and the gun moves back towards his shoulder 3rd

Name that Law 7. A boy wants to travel faster on his bike so he peddles with more force 2nd

How many of these are forces? Inertia Mass Friction Buoyancy Newtons Weight Compression Tension Equilibrium Distance Gravity Normal