Study these Key concepts for the Physics Quiz and Test:

  1. Work is performed when a force causes an object to move. If an object does not move, no work is done upon that object.
  1. Work is calculated by multiplying the force exerted on an object by the distance it moves in the direction of the force. (W=F x D).

For example: If a 40N box moved 10 meters, then 400J (Joules) of work was done on the box.

  1. Ramps, or inclined planes and other simple machines can reduce the amount of work force needed to move an object, but they do not change the amount of workdone. When the force is reduced, the distance is increased, so that the amount of work done remains the same.
  1. A force is a push or a pull. If both forces are going in the same direction, their forces add together. Ex. Ann pushes a box with a force of 50N and Tim pushes the box in the same direction as Ann with 50N of force as well. Their forces add up to 100 N and the box will move in the direction they are pushing it.
  2. Two types of Forces:
  3. Balanced-forces that cancel each other out. The two opposing forces are equal. Net force=0.

Examples: standing, sitting, tying at tug-of-war

  1. Unbalanced- forces that put an object in motion. The two opposing forces are not equal.

Examples: winning at tug-of-war because your team pulls it in the winning direction, walking down the hall and someone hits into you and causes you to change direction and stumble, hitting a tennis ball with a racket, pushing someone out of their chair.

  1. Friction
  2. Friction is the force that acts in the direction opposite to the motion of the moving object.
  3. Friction will cause a moving object to stop or slow down.
  4. Examples: pushing a box up an incline, tires on the road
  1. Compound machine –a device that combines two or more simple machines

Examples: scissors, bike, knife, electric pencil sharpener, etc.

Work-The product of force and distance when a force is used to move an object.
Joule-A unit of work equal to one newton-meter.
Machine-A device that changes the amount of force exerted, the distance over which force is exerted, or the direction in which force is exerted.
Input force-The force exerted on a machine
Output force-The force exerted on an object by a machine.
Mechanical advantage-The number of times the force exerted on a machine is multiplied by the machine.
Efficiency-The percentage of the input work that is converted to output work.
Actual mechanical advantage-The mechanical advantage that a machine provides in a real situation.
Ideal mechanical advantage- The mechanical advantage that a machine would have without friction.
Inclined plane-A simple machine consisting of a flat surface with one end higher than the other.
Wedge-A simple machine consisting of a device that is thick at one end and tapers to a thin edge at the other.
Screw-A simple machine that consists of an inclined plane wrapped around a central cylinder to form a spiral.
Lever-A simple machine consisting of a rigid object that pivots about a fixed point.
Fulcrum-The fixed point around which a lever pivots.
Wheel and axle-A simple machine consisting of two circular or cylindrical objects that are fastened together and rotate about a common axis.
Pulley-A simple machine consisting of a grooved wheel around which is wrapped a rope, chain, or cable.
Compound machine-A device that combines two or more simple machines.
Gears-Two or more wheels linked together by interlocking teeth.