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
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
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.