Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

(a) Radiant energy (b) Thermal energy

(c) Chemical energy (d) Nuclear energy (e) Electrical energy

The energy something possesses due to its motion, depending on mass and velocity.

Potential energy

Energy in Energy out

kinetic energy kinetic energy

Energy

Kinetic Energy – energy of motion

KE = ½ m v 2

Potential Energy – stored energy

Batteries (chemical potential energy)

Spring in a watch (mechanical potential energy)

Water trapped above a dam (gravitational potential energy)

mass velocity (speed)

B

AC

School Bus or Bullet?

Which has more kinetic energy; a slow moving school bus or a fast moving bullet?

Recall: KE = ½ m v 2

KE = ½ m v 2 KE = ½ m v

2

BUS BULLET

KE(bus) = ½ (10,000 lbs) (0.5 mph)2 KE(bullet) = ½ (0.002 lbs) (240 mph)2

Either may have more KE, it depends on the mass of the bus and the velocity of the bullet.

Which is a more important factor: mass or velocity? Why? (Velocity)2

Kinetic Energy and Reaction Rate

Kinetic energy

Fra

ctio

ns o

f pa

rtic

les

lower temperature

higher temperature

minimum energyfor reaction

Kinetic Energy and Reaction Rate

Kinetic energy

Fra

ctio

ns o

f pa

rtic

les

lower temperature

higher temperature

minimum energyfor reaction

Hot vs. Cold Tea

Kinetic energy

Many molecules have anintermediate kinetic energy

Few molecules have avery high kinetic energy

Low temperature(iced tea)

High temperature(hot tea)

Perc

ent o

f mol

ecul

es