What is work?

FORCE X DISTANCE (in the direction of the applied force). Measured in JOULES

If you drag a block 20m with 5N or force, how much work did you do?

100 newton meters, or 100 JOULES

IF WORK=FORCExDISTANCE, then DISTANCE=

WORK/FORCE

IF WORK=FORCExDISTANCE, then FORCE=

WORK/DISTANCE

If you do 10 joules of work over 5 meters, how much force?

WORK/DIST= FORCE so 10 Joules/ 5 meters = 2 NEWTONs

If you do 20 joules of work using 5N of force, how far did you go?

WORK/FORCE=DISTANCE so 20 joules/ 5 newtons= 4 meters

What is POWER? (two ways)

WORK/TIME or FORCE*DISTANC/TIME. It measures the rate of work, how fast you can do the work

What is ENERGY?

Ability to do work. Like stored work.

What are the units of ENERGY?

JOULES - think of it as “work waiting to be done” or “stored work”

How is work different from energy?

WORK is being done, Energy is work waiting to be done, like a battery wating to be used.

How is work different from power?

Work is force*distance, and power is an amount of work per unit of time. It is work/time. Power is a RATE OF DOING WORK, basically, how fast you can do the work.

What is the unit of work we use?

JOULE (newton*meter)

What is the unit of power we use?

WATT (joule/sec) or (newton*meter/second)

What is the unit of energy we use?

JOULE (newton*meter)

Explain FORCE units two ways

Newton or kg*m/s2

Explain POWER units three ways

WATT or joule/s or kg*m2/s3

Explain WORK units three ways

JOULE, or Nm, or kg*m2/ s2

What is potential energy?

mgh- non-moving stored energy. from HEIGHT.

What is kinetic energy?

one half mass velocity squared. MOVING energy.

You lift 8kg up 5 meters, How many JOULES?

400 Joules

You lift 8kg up 5 meters in 4 seconds, how many WATTS of power?

100 watts

You lift 8kg up 5 meters in 20 seconds, how many WATTS of power?

20 watts

there are ______ of FORCE, ____ of WORK ,______ of POWER and _____ of ENERGY

NEWTONS of force, JOULES of work, WATTS of power and JOULES of energy

EQN relating change in PE to change in KE

mg(delta h)= 1/2 m(delta v)2

Conservation equation

PEo+KEo = PEf +KEf or mgh+1/2 mv2 = mgh + 1/2 mv2 (notice the mass can cancel if it doesn’t change)

How much energy in a 25kg block 4meters high?

PE= mgh = 25*10*4 = 1000 J

How much energy in a 4kg block traveling 3 m/s

KE = mv2/2 = 4*3^2 / 2 = 36/2 = 18 J

How much power if you move 50 kg 20 meters in 10 seconds?

P = Fd / t = 50*20/10 = 100 WATTS

WATTS measure ____

Power

NEWTONS measure____

Force

JOULES measure _____

Work and Energy

What are the two energies we talk about in this unit?

Potential (height) and Kinetic (speed)