Motion is a change in position Speed is change in position over time Velocity is speed plus direction Acceleration is change is speed or velocity over timea = (v f - v i )/t +a is speeding up -a is slowing down

Newton’s 1 st law An object that is in motion will remain in motion until acted on by an outside force. What is Force? A Push or a Pull Push on your Science Book and it moves along the desk Push the same amount on a smaller book and it moves faster.

Newton’s 2 nd law A force acting on an object will cause that object to accelerate in the direction of the force. F = m x a a = F / m m = F / a Why don’t things keep going after you apply a force?

Friction Micro welds formed between the microscopic bumps of the surfaces.

Friction Static Friction The friction between two surfaces that are not moving past each other. Sliding Friction The force that opposes motion between two surfaces that are sliding past each other. Rolling Friction The frictional force between a rolling object and the surface it rolls on.

Air Resistance Friction that occurs between an object and the medium (air) that it is moving through. Like other forms of friction it acts in the opposite direction to the motion Air resistance (amount) depends on the speed, size and shape of the object rather than the mass. Terminal Velocity – the velocity where the force of air resistance is equal to the force accelerating the object.

Gravity The Law of Gravitation Anything that has mass is attracted to everything else that has mass. Gravity is one of the four basic forces in the Universe. Gravity – Attraction that varies with Mass and Distance Strong Nuclear and Weak Nuclear – Attraction that acts within the nucleus Electromagnetic – Electricity, Magnetism & Chemical reactions

Gravity The range of the force of gravity is the universe. Everything in the universe is attracted to everything else. The planet Neptune was found because of the affect of its gravity on the orbits of the other planets. The force of gravity follows the same formula F=m a Near the earths surface a = 9.8 m/s 2

Gravity Gravitational force on an object is the weight. Weight is measured in Newtons An object that masses 100 kg weighs 980 N Free Fall Objects that are falling at the rate of gravitational acceleration will appear to float. Astronauts seem to float because both they and the capsule they are in are falling toward the Earth at the same rate. At 1000km from the Earth’s surface the force of gravity is only ¾ of what it is at the surface

Gravity In a gravity field all projectiles follow a curved path. Centripetal Acceleration and Force Acceleration or force towards the center of the curve. Projectiles have both horizontal and vertical velocities at the same time. The Moon is constantly falling toward the Earth. The Earth is constantly falling toward the Sun.

Newton’s 3 rd law For every action there is an equal and opposite reaction Action and Reaction Forces act on different objects A swimmer pushes on the water and the water pushes them forward. Rocket Propulsion Hot gas is thrown out the back at high speed and the rocket moves in the opposite direction. Momentum A property of matter due to its mass and velocity p = m x v

Changing momentum over time is Force F = (mv f – mv i )/t Law of Conservation of Momentum After a collision of a cue ball with the rack on a pool table the total momentum of the pool balls equals the momentum of the cue ball at the moment it hit.