Work and Energy Definition of Work Kinetic Energy

Work and Energy Definition of Work Kinetic Energy Potential Energy Conservation of Mechanical Energy Power Efficiency

What is work? The product of Force and distance moved In the direction of the force

In the direction of the force Force and displacement must be in the same dimension Parallel or antiparallel If parallel, work done is positive If antiparallel, work done is negative If force is perpendicular to displacement, work done is zero.

Negative work is also referred to as Work done against the antiparallel force

F s Work = F x s Positive work Units for Work: Nm or Joule, J

Weight • Work done by • Weight • Zero • Normal • Zero • Friction • Negative Normal Force Tension Friction

No work for Gravity and Normal force s Work = (F cos 30) x s

Examples

How do you calculate for total work?

To calculate for total work Sum of all of the work done by each force Or Net force x displacement

Points on Total Work If net force is zero, total work is also zero. If net work is not zero, then the body is accelerating. Equation

What is energy? The stored ability to do work

Kinetic Energy of an object Stored ability to do work because of its motion. Work –Energy Theorem

Examples

The work done by gravity

Second case

(Gravitational) Potential Energy of an object Stored ability to do work as a result of it position. Conservation of Mechanical Energy

Examples

Power The rate of doing work Work done per unit time Equation Units

Power and Quality of work are not the same.

Efficiency Power output per power input

Example A simple pendulum, consisting of a mass m, is attached to the end of a 1. 5 m length of string. If the mass is held out horizontally, which makes a 60°angle with the vertical, and then released from rest, what is its speed at the bottom?

Example If the 1000 - kg roller coaster leaves Point Q from rest, how fast is it traveling at Point R?

Example If the 1000 -kg roller coaster leaves Point Q from rest, what is its speed at Point S?

Past Paper Example

Past Paper Example

Past Paper Example