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Kinetic and Potential EnergyKinetic and Potential Energy
It’s “Natural Money”It’s “Natural Money”
From the Parable of the Lost PennyFrom the Parable of the Lost Penny
Conservation of EnergyConservation of Energy
Kinetic and Potential EnergyKinetic and Potential Energy
Kinetic and Potential EnergyKinetic and Potential Energy
© 2013 Pearson Education, Inc.
A child is on a playground swing, motionless at the highest point of his arc. What energy transformation takes place as he swings back down to the lowest point of his motion?
QuickCheck 10.1
A. K Ug
B. Ug K
C. Eth K
D. Ug Eth
E. K Eth
Slide 10-27
© 2013 Pearson Education, Inc.
A child is on a playground swing, motionless at the highest point of his arc. What energy transformation takes place as he swings back down to the lowest point of his motion?
QuickCheck 10.1
A. K Ug
B. Ug K
C. Eth K
D. Ug Eth
E. K Eth
Slide 10-27
© 2013 Pearson Education, Inc.
Energy Bar Charts
A pebble is tossed up into the air. The simple bar charts below show how the sum of K + Ug
remains constant as the pebble rises and then falls.
Slide 10-34
© 2013 Pearson Education, Inc.
Rank in order, from largest to smallest, the gravitational potential energies of the balls.
A. 1 > 2 = 4 > 3
B. 1 > 2 > 3 > 4
C. 3 > 2 > 4 > 1
D. 3 > 2 = 4 > 1
QuickCheck 10.4
Slide 10-38
© 2013 Pearson Education, Inc.
Rank in order, from largest to smallest, the gravitational potential energies of the balls.
A. 1 > 2 = 4 > 3
B. 1 > 2 > 3 > 4
C. 3 > 2 > 4 > 1
D. 3 > 2 = 4 > 1
QuickCheck 10.4
Slide 10-39
© 2013 Pearson Education, Inc.
Gravitational Potential Energy on a Frictionless Surface
The total mechanical energy for a particle moving along any frictionless smooth surface is conserved, regardless of the shape of the surface.
Slide 10-48
© 2013 Pearson Education, Inc.
Starting from rest, a marble first rolls down a steeper hill, then down a less steep hill of the same height. For which is it going faster at the bottom?
QuickCheck 10.5
A. Faster at the bottom of the steeper hill.
B. Faster at the bottom of the less steep hill.
C. Same speed at the bottom of both hills.
D. Can’t say without knowing the mass of the marble.
Slide 10-49
© 2013 Pearson Education, Inc.
Starting from rest, a marble first rolls down a steeper hill, then down a less steep hill of the same height. For which is it going faster at the bottom?
QuickCheck 10.5
A. Faster at the bottom of the steeper hill.
B. Faster at the bottom of the less steep hill.
C. Same speed at the bottom of both hills.
D. Can’t say without knowing the mass of the marble.
Slide 10-50
© 2013 Pearson Education, Inc.
Three balls are thrown from a cliff with the same speed but at different angles. Which ball has the greatest speed just before it hits the ground?
QuickCheck 10.7
Slide 10-57
A. Ball A.
B. Ball B.
C. Ball C.
D. All balls have the same speed.
© 2013 Pearson Education, Inc.
Three balls are thrown from a cliff with the same speed but at different angles. Which ball has the greatest speed just before it hits the ground?
QuickCheck 10.7
Slide 10-58
A. Ball A.
B. Ball B.
C. Ball C.
D. All balls have the same speed.
© 2013 Pearson Education, Inc.
FRQ Practice
2. A roller coaster car of mass 650 kg is moving with a velocity of 15 m/s at the top of the first hill of a roller coaster track as shown in the diagram. The cart rolls without friction down the hill and through a vertical circular loop of radius 12 m.
(a) Calculate the maximum velocity of the roller coaster.
© 2013 Pearson Education, Inc.
(b) The roller coaster travels without friction through the circular loop
i. On the diagram below, draw and label all of the forces acting on the roller coaster when it is upside down at the top of the loop
ii Calculate the magnitude of the normal force exerted on the roller coaster when it is upside down at the top of the loop
iii. The safety engineer determines that the acceleration of the riders is too great while they are passing through the loop. Describe a way the engineer can modify the ride to safely reduce the acceleration of the passengers as they go through the loop. Justify your answer.
