Chapter 15.2- Energy Conversion and Conservation (15 pts total) 1. Complete the thinking map after reading pg. 453 of the text. Explain how the gull gets the oyster out of the shell using energy conversions. (2 pts) Fill in the Blank (1 pt each)

2. When a wind up toy is set in motion, elastic potential energy that was stored in the compressed spring is converted into the ______________________________ of the toy’s moving parts.

3. What does the law of conservation of energy state? ________________________________ ____________________________________________________________________________. 4. A moving object slows down because friction causes a continual conversion of kinetic

energy into ________________________________. 5. As an object falls, the gravitational potential energy of the object is converted into

____________________________________ 6. During a pole-vaulter’s jump, when is his gravitational potential energy the greatest?

__________________________________________________________________________ 7. What type of energy increases as the pole bends before it propels a pole-vaulter up into the

air? _________________________________ 8. What type of energy change results when friction slows down an object?

____________________________ to ______________________________ 9. What type of energy conversion is occurring when gasoline powers an engine? ________________________________ to ________________________________ 10. What does Einstein’s equation imply about mass and energy? ________________________ _____________________________________________________________________________

Matching: What type of energy is described in the situations below. (1 pt each) Situation Form of energy

11. A stationary wind-up toy with a compressed spring

12. A descending roller coaster car 13. A car driving on a flat road 14. A vibrating guitar string 15. A skier poised to take off at the

top of a hill

a. Kinetic energy b. Potential energy c. Both

Energy

Gull lifts the oyster into the air. KE of the gull lifting the oyster into the sky is converted into GPE.

How Gulls use Energy Conversions

At max height the gull drops the oyster. _________________________________________________________________________

At max speed when the oyster hits the rocks. _________________________________________________________________________________

Chapter 15.2- Problem Solving: Energy Conservation (18 pts total) Conservation of Mechanical Energy (KE + PE)beginning = (KE + PE)end Example: A 1.25 kg stone fell from a cliff and struck the ground at a speed of 29.4 m/sec. What was the gravitational potential energy (GPE) of the stone before it fell? First….

(KE + PE)beginning = (KE + PE)end

(0 + PE) beginning = (KE + 0)end

PE beginning = KEend Therefore…. Step 1- Step – 2 Step – 3

KEend = ½ mv2 KE = ½ (1.25 kg) (29.4)2 KE = 540 J Then…. Step 1- Step – 2 Step – 3 PE beginning = KEend PEbeginning = KEend = 540 J PEbeginning = 540J Practice with problem solving (6 pts each problem) Directions: Show 3 step solution for all problems. Must show units in ALL calculations. Step 1: Write out formula Step 2: Plug in the information Step 3: Solve the problem

1. A 0.2 kg object is lifted into the air and then dropped to the floor. If it is moving at a speed of 3 m/sec when it hits the floor, what was its gravitational potential energy before it was dropped? (hint: very similar to the example above)

Step 1- Step – 2 Step – 3 Step 1- Step – 2 Step – 3

2. A 56 kg person attached to a bungee cord jumps off a 10 meter high tower. What is her kinetic energy when she reaches the bottom of her fall? (hint: this time solve for PE first)

Step 1- Step – 2 Step – 3 Step 1- Step – 2 Step – 3

3. Lance, who has a mass of 60 kg, jumped off a retaining wall. His kinetic energy when he landed on the ground was 882 joules. How high was the wall? (hint: solve PE formula for h)

Step 1- Step – 2 Step – 3 Step 1- Step – 2 Step - 3

Given info: KEbeginning = 0 PEend = 0 Mass = 1.25 kg Velocity = 29.4 m/sec