Click on the question number below 115 116 117 118 119 120 121 122 Solutions to momentum and energy problems Kinetic energy Intermediate 2 Mechanics and Heat ID: 934994
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Slide1
Physics Support Materials
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115, 116, 117, 118, 119, 120, 121, 122
Solutions to momentum and energy problemsKinetic energy
Intermediate 2 Mechanics and Heat
Slide2Physics Support Materials
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Calculate the kinetic energy of the following:
a) a 5 kg bowling ball moving at 4 m/s
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
115
b) a 50 kg skier moving at 20 m/s
c) a 0.02 kg bullet moving at 100 m/s
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a) How much kinetic energy does a 800 kg car have at a speed of 10 m/s?
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
116
b) If it doubles its speed to 20 m/s, calculate its new kinetic energy
.
Note: doubling the speed increases the kinetic energy by four
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A cyclist who is pedalling down a slope reaches a speed of 15 m/s. The cyclist and her cycle together have a mass of 80 kg.
a) Calculate the total kinetic energy.
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
117
b) Name two sources of this kinetic energy.
i) Gravitational potential energy
ii) Chemical energy (during the conversion of energy in the muscles)
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Calculate an
approximate value for the kinetic energy of an Olympic 100 m sprinter as he crosses the line (time for race is about 10 s).
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
118
Estimate mass of athlete to be 70 kg
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What is the speed of a stone of mass 2 kg if it has 36 J of kinetic energy?
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
119
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A motor cyclist and his bike have a total mass of 360 kg and kinetic energy of 87120 J. What is his speed?
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
120
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The apple in question 112 is dropped from the top of the Eiffel Tower.
a) How much kinetic energy would it have just before hitting the ground?
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
121
Kinetic energy gained = Potential energy lost =300 J
b) What will be its velocity as it hits the ground?
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A car of mass 1000 kg is travelling at 20 m/s.
a) How much kinetic energy does it have?
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
122
b) If the maximum breaking force is 5 kN, what will be the minimum breaking distance?
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c) If the driver has a reaction time of 0.7 s, how far will the car travel during
his “thinking time”?
Intermediate 2 Mechanics and Heat
Momentum and Energy
/ Kinetic Energy
122 (continued)
d) What will the total stopping distance be?
Total stopping distance = “Thinking distance” + Breaking distance
= 14 m +40 m
= 54 m