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).
Jul 08, 2015
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.