Tuesday May 21. Overview Energy 1.Motion 2.Object 3.Potential 4.Mechanical Energy 5.Chemical 6.Elastic 7.Chemical 8.Gravitational 9.Elastic 10.Gravitational.

Tuesday May 21

Overview Energy1. Motion2. Object3. Potential4. Mechanical Energy5. Chemical6. Elastic7. Chemical8. Gravitational9. Elastic10.Gravitational

The nature of energy

1. Energy of a spinning bicycle wheel

2. Energy stored in food3. Energy stored in a

boulder on a ….4. Energy stored in a

stretched string5. Energy that is stored

6. Less7. More8. Energy9. Joule10. Potential,kinetic11. Potential12. Chemical

Chapter Test Continued

18) A19) D20) B21) C22) A23) B24) D25) C

Understanding Concepts1. A. PE=mgh=10(9.8)

(1.5)=147 J B. PE=mgh=(10)(9.8)(1)= 98

J2. KE= ½ mv2= .5(10)(10)(10)=

500 J3. KE=PE=147 J

There are two types of potential energy problems.

A 4.5 kg dictionary sits on a 4.0 m high shelf. Find its potential energy.

• PE= mgh• PE= 4.5 (9.8) 4• PE= 176.4 J

A 12-N copper ball sits on a church stepple 40 m above the ground. Find its potential energy.

• PE=WH• PE= 12(40)• PE=480 J

An automobile to be transported by ship is raised 7.0 m above the dock. If its gravitational potential energy is 66000 J, find its mass.

• Given • Solution

An automobile to be transported by ship is raised 7.0 m above the dock. If its gravitational potential energy is 66000 J, find its mass.

• GivenH= 7.0 mA= 9.8 m/s/sPE= 66 000 JM= ?

• Solution• PE=mgh• M=PE/gh• M= 66 000/9.8(7)• M= 960 kg

The world record for pole vaulting is 6.15 m. If the athlete’s

gravitational potential energy is 4,942 J, what is his mass?

• Given • Solution

The world record for pole vaulting is 6.15 m. If the athlete’s

gravitational potential energy is 4,942 J, what is his mass?

• Given• H= 6.15 m• PE= 4942 J• G= 9.8 m/s/s• M=?

• Solution• PE=mgh• M=PE/gh• M= 4942/9.8(6.15)• M= 82 kg

Find the kinetic energy of a .045 kg hockey puck traveling at 45 m/s.

• KE= ½ mv2

• KE= ½ (.045) (45)(45)• KE= 45.56 J

A baseball is pitched with a speed of 35 m/s. Calculate its kinetic

energy if it has a mass of 0.146 kg?

• Given • Solution

A baseball is pitched with a speed of 35 m/s. Calculate its kinetic

energy if it has a mass of 0.146 kg?

• Given• M= 0.146 kg• V= 35 m/s• KE= ?

• Solution• KE= ½ mv2

• KE= (.5)(0.146)(35)(35)• KE= 89 J

A “ping-pong” ball has a mass of .00245 Kg and can be given a

speed of 4.0 m/s. Find its kinetic energy?

• Given • Solution

A “ping-pong” ball has a mass of .00245 Kg and can be given a

speed of 4.0 m/s. Find its kinetic energy?

• Given• M= 0.00245kg• V= 4 m/s• KE= ?

• Solution• KE= ½ mv2

• KE= (.5)(0.00245)(4)(4)• KE= 0.0196 J

Potential Energy Worksheet

• 1. PE=mgh or PE=WH• 2. Joule (J)

3. PE=WHPE=12(21)PE=252 J

Potential Energy Worksheet

4. PE=WHPE=79(20)PE= 1580 J

5.PE=WHPE=190(45)PE=8550 J

Potential Energy Worksheet

6.PE=WHPE= 966(72)PE= 69, 552 J

7.PE=mghPE=5(9.8)12)PE= 588 J

Kinetic and Potential Energy Worksheet

1 KE= ½ mv2

• KE= ½ 2.1(30*30)• KE= 945 J

3 KE= ½ mv2

• KE= ½ (1120) 40 * 40• KE= 8,960,000 J

Kinetic and Potential Energy Worksheet

7. D8. A9. D10.Friction.

Energy problems Worksheet

• 1. KE= ½ mv2

• KE= = .5(3) (5)(5)

• KE= 37.5 J

Energy problems Worksheet

• 2. PE=mgh• PE= 6.5(9.8)(5)• PE=166 J

Energy problems Worksheet

• KE= ½ mv2

• M= 2 KE/v2• M= 2(173)/(3.8 * 3.8)• M= 24 J

Energy problems Worksheet

• PE=mgh• H=PE/mg• H=328/(7.5)(9.8)• H=4.5m

Energy problems Worksheet

• 5.• KE= ½ mv2

• KE= ½ 30 (2*2)• KE= 60 J• KE= ½ mv2

• KE= ½ 60 (2*2)• KE= 120 J• It doubles.

Energy problems Worksheet

• 6. • KE= ½ mv2

• KE= ½ 30 (2*2)• KE= 60 J• KE= ½ mv2

• KE= ½ 30 (4*4)• KE= 240 J• It is quadrupled.

•

Energy problems Worksheet

• 7.PE= mgh PE= 4(9.8)(2) PE=78.4 J J PE=mgh PE= 4(9.8)(4) PE= 156.8 J

It doubled.

Energy problems Worksheet

• 8.• KE= ½ mv2 . 4.2 m/s

• KE= ½ 12 (3*3)

Energy problems Worksheet

• 9.• KE= ½ mv2

• 2KE= m (52*52)• m= 72 kg

Energy problems Worksheet

10. PE= mgh PE= 0.49(9.8)(3.6) PE=17.3 J PE=mgh PE= 0.49(9.8)(1.5) PE= 7.2 J Decreased by 10.1 J