Chapter 13 – Forces in Motion

Types of Motion Constant Motion – motion that is constant and steady

Types of Motion Variable Motion – motion that moves in many directions and at many speeds

Types of Motion Periodic Motion – back and forth steady movement

Types of Motion Circular Motion – movement in circles

Types of Motion Vibrational Motion – movement that is quick, back and forth vibrations

Speed The distance an object travels in a certain amount of time. The distance an object travels in a certain amount of time. To find the speed divide the distance and the time it took to go that distance To find the speed divide the distance and the time it took to go that distance S = D/T S = D/T Sammy the Snail Sammy the Snail Sammy the Snail Sammy the Snail

Velocity Describes the speed and direction of an object’s motion. Example: The plane is moving west at 300mph. Speed and Velocity

Point of Reference Motion measured as a relationship between two objects. Reference point

Force A push or a pull that acts on an object. A push or a pull that acts on an object. Forces can make a moving object speed up, slow down, or change directions. Forces can make a moving object speed up, slow down, or change directions.

Gravity The force of attraction between two objects causing them to have weight. The force of attraction between two objects causing them to have weight. Examples Examples Apple falling out of a tree. Apple falling out of a tree. Skydiver landing on the ground. Skydiver landing on the ground.

Magnetism A force that pushes and pulls on other objects A force that pushes and pulls on other objects Push – two north poles will push away from each other Push – two north poles will push away from each other Pull – a north pole and a south pole will pull toward each other Pull – a north pole and a south pole will pull toward each other

Electricity All objects that are electrically charged will exert forces on each other. All objects that are electrically charged will exert forces on each other. Oppositely charged objects are attracted to each other. Oppositely charged objects are attracted to each other. Objects with the same chare are repelled, and move away from each other Objects with the same chare are repelled, and move away from each other

Friction The force between moving parts that tends to slow them down. The force between moving parts that tends to slow them down. Magic School Bus – Plays Ball Magic School Bus – Plays Ball

Work Work is done when a force moves an object. Work is done when a force moves an object. If the force does not make the object move, then no work has been done If the force does not make the object move, then no work has been done Work is done only when the object moves Work is done only when the object moves Scientific DefinitionFormula Work (Joules) Energy used when a force moves an object Work = force x distance

Power The rate at which work is done. The rate at which work is done. Walking up a hill and running up the same hill take the same amount of work. Since running up the hill is faster than walking, the amount of power needed to run is greater. Walking up a hill and running up the same hill take the same amount of work. Since running up the hill is faster than walking, the amount of power needed to run is greater. Scientific DefinitionFormula Power (Watts) Rate at which work is done Power = work/time

Newton’s Laws of Motion The Science of Sports The Science of Sports

Newton’s 1 st Law of Motion An object at rest stays at rest until a force acts on it. An object moving at a constant speed will continue to move in a straight line and at a constant speed until a force acts on it. An object at rest stays at rest until a force acts on it. An object moving at a constant speed will continue to move in a straight line and at a constant speed until a force acts on it.

Inertia The tendency of an object to resist any change in motion The tendency of an object to resist any change in motion The physical property that keeps an object moving after the accelerating force is gone. The physical property that keeps an object moving after the accelerating force is gone.

Newton’s 2 nd Law of Motion Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

Acceleration The rate at which the velocity of an object changes over time. The rate at which the velocity of an object changes over time.

Newton’s 3 rd Law of Motion For every action there is an equal and opposite re-action. For every action there is an equal and opposite re-action.

Air Resistance The force that acts to slow down any object moving through air. The force that acts to slow down any object moving through air.

Pulley A pulley consists of a rope or cable that runs through a grooved wheel. A pulley consists of a rope or cable that runs through a grooved wheel. Makes work easier by changing the direction of the force Makes work easier by changing the direction of the force Examples – flagpole, window blinds Examples – flagpole, window blinds

Wheel and Axle A wheel and axle is made up of a circular object and a shaft. A wheel and axle is made up of a circular object and a shaft. Examples – doorknob, bicycle wheel Examples – doorknob, bicycle wheel

Lever A lever is a stiff bar rotating around a fixed point called a fulcrum. A lever is a stiff bar rotating around a fixed point called a fulcrum. Makes work easier by changing the direction of a force. Makes work easier by changing the direction of a force. Examples – hammer, shovel Examples – hammer, shovel

Inclined Plane An inclined plane consists of a flat surface with one end higher than the other. An inclined plane consists of a flat surface with one end higher than the other. Examples – wheelchair ramp, playground slide Examples – wheelchair ramp, playground slide

Screw An incline planed wrapped around a center rod An incline planed wrapped around a center rod Examples – base of jar lid, light bulb base Examples – base of jar lid, light bulb base

Wedge A wedge is two inclined planes placed back to back A wedge is two inclined planes placed back to back Examples – knife, axe, fork, nail, doorstop Examples – knife, axe, fork, nail, doorstop