physics final

work

The ability to do work

• Nm = j

• scalar

if an object is not moving is work being done

no

examples

• holding an object

  • d = 0

• carrying a box down a halway

  • d = 0

  • cos(90) = 0

if the force is parallel to displacement then w =

F (delta x)

• cos(0) = 1

angles between 90 and 270 have forces with components the motion

against and work is negative

kinetic energy observations

• if there is a net force then there is acceleration

• acceleration means change in velocity

• scalar

• depends on speed not position

conservative force definition

• a force is conservative if the work done by (or against) the force in moving an object is independent of the path of the object is independent of the path of the object

conservative forces

• work does not depend on path

examples

• force of gravity

• spring forces

Non-conservative forces

adds or removes mechanical energy from a system

• work depends on path

examples

• frictions force

• air resistance

potential energy

energy stored in an object due to its position

• assoiciated w/ conservative forces only

• change in conservative energy= work done against a conservative force

• lost as objects fall to the ground

• J

work does not depend on

speed

if force acts at 90-degrees/ perpendicular to the direction of motion to the direct of motion is work being done

no

If the mass of an elevated object is doubled then its gravitational potiental energy will

doubled

the higher an object is the …….. potential energy it will have

more

if the speed of an object is doubled, the kinetic energy is

quadrupled

if the mass of a moving object is halved, the kinetic energy is

halved

if the mass of an object is doubled, the gravitational potential energy is

doubled

if the force of on a spring is doubled, the stretch of a string is

doubled

if the stretch of a spring is halved, the spring potentail energy is

quartered

simple machines

are devices that can be used to multiply (or reduce) a force that we apply – at the expense of a distance through which we apply the force.

• do not do any work just make it easier

Simple Machines

• Inclined plane

• Pulley

• Lever

• Wheel and axle

• Jackscrew

• Wedge