Ch. 13 Force and Motion. How can you describe motion?. Types of motion: constant (Earth) vibrational (guitar string) variable (cars, trucks) circular (car tire) periodic (pendulum). Speed and Velocity. Average speed = divide Distance and Time
The monorail at Disney moved 100 meters in 20 seconds. What is the average speed?
100 m =
20 s Answer: 5 m/s
Rubbing a balloon against your hair will create enough
static charge to make the balloon ‘stick’ to a wall.
**In space there is less friction than Earth. This means that a satellite moving around Earth will not slow down much.
An object in motion stays in motion
An object at rest stays at rest
A net force acts on the object.
The acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object.
The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.
**The action-reaction law of motion.
When an object exerts a force on another object, the second object exerts a force on the first object.
Ex. Person leaning on a wall, hammer pounding a nail into a board
Scenario: A satellite orbiting Earth is knocked out of its orbit by a meteor
1st law: Satellite remained in orbit because an object in motion stays in motion.
2nd law: The force of the meteor caused a change in the motion of the satellite.
3rd law: The force of the meteor hitting the satellite is equal and opposite to the force of the satellite hitting the meteor.
Wheel and axle
Ex. Go cart, sailboat, screw, car engine, airplane
Why a screw?
It consists of metal rod with an inclined plane wrapped around it, and changes direction and the amount of force needed.