Insta - freeze

When gases expand,
they absorb internal energy

Ex 3) Pendulum

Click on a length to start pendulum

| Full Size |
St. Mary's Physics

If PE at A = 10 J, KE = 0

	PE	KE
A	10 J	0 J
B	0 J	10 J
D	10 J	0 J

If PE at C = 3 J, KE = ?

KE = 7 J

Wind turbines convert

one form of energy into

another. What is that

conversion?

Wpclipart

Kinetic energy to

electric energy.

All Pendulums

PE Max. at

Extremes

KE Max. at

Bottom

PE at Extremes

KE at Bottom

KE @ Extreme

Zero

PE @ Bottom
always

Zero

Ex 4) 1.0 kg pendulum swings to a height of .20 m above its lowest point.

K.E. of pendulum at lowest point?

Ex 4) 1.0 kg pendulum swings to height of .20 m above lowest point. KE of pendulum at lowest point?

PE @ A

=

KE @ B

PE = mgh

= (1.0 kg)(9.8 m/s²)(.20 m)

PE = 2.0 J

PE = KE @ B = 2.0 J

Ex 5) 5.00-kg cart at foot of a hill 10.0 m high. For cart to reach the top of the hill, what is minimum KE of cart in the position shown?

[neglect friction.]

Ex 5) 5.00-kg cart at foot of hill 10.0 m high. For cart to reach the top of the hill, what is minimum K.E. of the cart in the position shown? [neglect friction.]

m = 5.00 kg

h = 10.0 m

KE = ?

KE at bottom = PE at 10.0 m

KE = PE = mgh

= 5.00 kg(10.0 m/s²)10.0 m

KE = 500. J

Author H. Christiaen, K.U.Leuven, Belgium

Energy Problems

Enrichment

Pendulum Top View

Foucault's Pendulum - Proved the earth rotates

Foucault_PendulumReal.wmv

Pendulum mounted on a rotating base

| Foucault_Pendulum.mpg | Foucault_Pendulum.wmv |