In terms of motion, what does energy allow you to do? Units?

How much work is done in each…? A man squats 200 kg masses a distance of 0.5 m. A waiter carries a 10 kg tray 10 m across the room. A 65 kg woman skies down from the top of Schweitzer (el. 1951m) to the lodge (el. 1220m). A child pulls on a rope with 10 N, dragging a block 10 m across the floor which the rope makes a 30 o angle to.

Force and Distance have to be in the SAME DIRECTION WORK ≡ Force · Distance 1000 N 6meters 6 meters How much WORK is done by the fork lift? Force DistanceZERO! W = f · d

Force and Distance have to be in the SAME DIRECTION WORK ≡ Force · Distance How much WORK is done by the fork lift? 1000 N 1.5 meters Force Distance Work = force · distance

600 N 5 m How much WORK does the runner do? 3 m Work = F * d

How much WORK do these fitness buffs do as they enter the gym?

In order to do “Work” what must be expended? What kinds of energy are there? _pancakes_large.jpg images/my_art/fullcolor/daring_01.jpg Work expended = Energy required/given

Who did more WORK? Which required more energy? How can they be equal?... Isn’t something different? Time is different… so…

UNITS= Watts POWER ≡ WORK Time Joules Second = Force·Distance Time =

40 WattMeans… A 40 Watt light bulb Means… 40 JoulesWORK 40 Joules of WORK done every second.

The energy in a BIG MAC could run the 40 W bulb for…

550 pounds 1 foot1 second An average horse can lift 550 pounds a distance of 1 foot in 1 second. 1 Horsepower ≡ 550 ft·lbs/s 1 ft/s 550 lbs. James Watt all day long. And do it all day long.

FIELD TRIP Clifton Bluhm Calculate YOUR Horse Power

80 ft How much time will it take the 2000 lb car to climb the 80 ft hill if the engine is 115 Hp? 115 Hp 550 = 63,250 1 Hp 1 Hp ft·lbs s POWER = Force·Distance Time 63,250 = 2,000 · 80 Time Time = 2.53 s

ENERGY ≡ The ability to do... WORK An object that has 100 Joules of E EE ENERGY has the ABILITY to do 100 Joules of W WW WORK ** Energy is conserved! **

POWER ≡ POWER ≡ Work Time POWER is how quickly WORK is done. POWER is how quickly ENERGY is expended. Energy Time ≡

The Work – Energy connection (in motion) 10,000 N of force applied for 10 m… how much work? How much energy does the bus now have? W done = ΔE Energy appears to be based on velocity… Let’s substitute in velocity somehow…

KE = ½mv 2 A 1000 kg car is traveling at 25 m/s… how much work must be done to stop it? If the F f has a max value of 10,000 N… what is the shortest distance that car can stop in?

The Work – Energy connection (potential) 2,000 N 40 m The box has potential… the potential to become KE. ** How calculate its Potential??? ** How much KE at the bottom??? – what is “v”???

PE g = mgh A 50 kg object hits the ground at 30 m/s… how high was it dropped from?

kg car KE = ½ m·v 2 WORK = F · d Velocity (m/s) Kinetic Energy Work Needed to Stop Stop Dist. Needed Assume the friction force is 10,000 N.

KE & PE applied… “But officer… I was only going 10 over?”