Motion and Forces
Motion
Forces
Gravity, Friction, and Pressure
Work and Energy
Machines
An object in motion changes position.
Position describes the location of an object.
Describing a Position
Measuring Distance
Standard unit of length is the meter (m), which is 3.3 ft.
Motion is a change in position.
Describing Motion
Relative motion
How an observer sees your motion depends on how it compares with his own motion.
Speed measures how fast position changes.
Position can change at different rates.
Calculating speed
s = d/t
speed is distance divided by time
Average speed
Distance-TIme Graphs
Velocity includes speed and direction
Velocity
Velocity vs Speed
Acceleration measures how fast velocity changes.
Speed and direction can change with time.
Acceleration can be calculated from velocity and time.
Calculating Acceleration
acceleration = final velocity - initial velocity / time
Acceleration over Time
Velocity-Time Graphs
Forces change motion.
A force is a push or a pull.
Types of Forces
Contact Force
Gravity
Friction
Size and Direction of FOrces
Balanced and Unbalances Forces
Forces on Moving Objects
Newton's first law relates force and motion.
Galileo's Thought Experiment
Newton's FIrst Law
Objects at rest remain at rest, and objects in motion remain in motion with the same velocity, unless acted upon by an unbalanced force.
Inertia
Force and mass determine acceleration.
Newton's second law relates force, mass, and acceleration.
Newton's second law
The acceleration of an object increases with increased force and decreases with increased mass.
Force = mass * acceleration (F = ma)
Mass and Acceleration
Forces can change the direction of motion.
Centripetal Force
Circular Motion and Newton's 2nd Law
Forces act in pairs
Gravity is a force exerted by masses.
Friction is a force that opposes motion.
Pressure depends on force and area.
Pressure describes how a force is spread over an area.
Pressure = force / area (P = F/A)
Fluids can exert a force on objects.
Work is the use of force to move an object.
Force is necessary to do work.
Work = Force * distance (W = Fd)
Objects that are moving can do work.
Energy is transferred when work is done.
Work transfers energy.
Work changes potential and kinetic energy.
GPE = mgh
KE = 1/2mv^2
ME = PE + KE
The total amount of energy is constant.
Power is the rate at which work is done.
Power = work / time (P = W / T)
Power = Energy / time (P = E / t)
Machines help people do work.
Six simple machines have many uses.
Modern technology uses compound machines.
Machines change the way force is applied.
Mechanical Advantage = Output Force / Input Force
Output work is always less than input work.
Efficiency = output work / input work *100
Lever
Wheel and axle
Pulley
Inclined plane
Wedge
Screw
MA = ^F out / ^F in
Ideal Mechanical Advantage = length of incline / height of incline (IMA = l/h)