Power, Work and Energy

PhysicsJanuary 2 and 3

Objectives

• Define and Describe work, power and energy• Evaluate how work, power and energy apply

to the real world• Solve for work, power and energy

What is work?

TopicWork

Facts• The application of a

force and the movement of something by that force (distance)

• Work = force x distance• W = Fd– F = force (N)– d = distance (m)–W = work (J)

Now think about the math of work

TopicWhat do you need to find

work?

What will the units for work be when solving?

What would you do if given the mass and distance to find work?

Facts• Force (N)• Distance (m)

• Joules (J)

• First use the mass to find for (F = w = mg).

• Then use the F and d to solve for work

What about Power?

TopicPower

Facts• The rate at which work

is done• Units are watts (W)• Power = work time• Power = W/t–W = work (J)– t = time (s)– Power (W)

Consider the math with Power

TopicTo solve for power,

what do you need?

How do you find work if it is not provided?

Facts• Work and time

• Multiply force and distance

What is Energy?

TopicEnergy

Facts• The “something” that

enables an object to do work

• Measured in Joules (J)

• We will focus on mechanical energy

What is Mechanical Energy?

TopicMechanical energy

Facts1. Potential energy– The energy due to

the position

2. Kinetic energy– the movement of

something

Potential Energy

TopicPotential energy

Facts• Energy stored and held in

readiness– Something at rest– Something high off the ground

• Symbol is PE• Units are Joules (J)• PE = mgh

– m = mass (kg)– g = gravity (10 m/s2)– h = height/distance (m)– PE= potential energy (J)

Kinetic Energy

TopicKinetic energy

Facts• Energy of motion• Symbol is KE• Units are Joules (J)• KE = ½ m(v2 )–m = mass (kg)– v = velocity (m/s)– KE = kinetic energy (J)

Work-Energy Theorem

TopicWhat is the

relationship between work and energy?

Facts• Whenever work is

done, energy changes• Work = change in Energy

Conservation of Energy

TopicWhen is energy

conserved?

Facts• ENERGY IS ALWAYS

CONSERVED!• Energy is transferred

from PE to KE and vice versa

Closing

TopicWhat is energy and how

does it relate to work and power. Be sure to use the following terms in your explanation

• KE• PE• Work• Power

Facts