Obj 3 forces that act on objects resulting in motion

Applications of forces

• Work: is done only when force applied to an object actually moves the object. Measured in joules (J).

• Force: is anything that causes a change in motion. Measured in Newtons (N).

• Effort: Is the amount of force you apply to get work done. Measured in kilograms (kg).

• Distance: is the amount of space an object moves. Measured in meters (m).

Work with a Machine

• WORK STAYS THE SAME!!!!

• Force is decreased. Less effort is applied. It is easier for work to be done.

• Distance increases.

Without a machine

• WORK STAYS THE SAME!!!!

• Force increases. More effort is necessary. It is harder for work to be done

• Distance decreases.

Levers

• A simple machine consisting of a bar that pivots at a fixed point, called a fulcrum.

• There are three classes of levers

1st Class

• The FULCRUM is always in between the input force and the out put force.

• Mechanical Advantage: <1, =1, >1

• Examples: Crowbar, scissors, rowboat, teeter totter.

2nd Class

• The OUTPUT FORCE (LOAD) is always between the fulcrum and the input force.

• Mechanical Advantage: >1 (greater than one)

• Examples: Bottle opener, wheel barrow.

3rd Class

• The INPUT FORCE is always between the fulcrum and the output

force (load).

• Mechanical Advantage: <1

(less than one)

• Examples: Barbells, hammer

Fishing pole.

Types of Friction

• Static Friction: when a force is applied to an object, but does not make it move

Types of Friction

• Sliding: it opposes the movement of objects that are sliding.

Types of Friction

• Rolling: a force that opposes a rolling object on another surface. It is less than sliding friction, so it is easier to move objects.

Types of Friction

• Fluid: it opposes motion of objects traveling through a liquid or gas.

Air Resistance

• It is fluid friction. It helps things fall more slowly.

Changing Force and Motion

• Isaac Newton came up with three laws that explain why objects move or don’t move.

Changing Force and Motion

• 1st Law: an object at rest remains at rest and an object in motion remains in motion at a constant speed and in a straight line unless acted on by an unbalanced force.

Changing Force and Motion

• 2nd Law: the acceleration of an object depends on the mass of the object and the amount of force applied.

• 3rd Law: whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.