A student on a bicycle moves at a speed of 18.8 mi/h. The total mass of the student and the bicycle is 88.8 kg. The student starts to slow down and comes to rest at a stop light. What is the amount of energy that was converted into heat during the slowing down?
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The friction force in the brakes is causing the bicycle to slow down. As the velocity of bicycle decreases to 0 m/s, its kinetic energy decreases to 0 J. The amount of energy that was converted into heat during the slowing down is equal the initial kinetic energy of the student and bicycle.
Let’s convert the speed to m/s. 1
1 mile = 5280 ft/mi * 12 in/ft * 2.54 cm/in * 0.01 m/cm = 1609.344 meters
1 hour = 3600 seconds
1 mi/h = 1609.344/3600 = 0.44704 m/s
This is usually rounded to 0.447 m/s
Speed = 18.8 * 0.447 = 8.4036 m/s
Initial KE = ½ * 88.8 * 8.4036^2
The amount of energy is approximately 3135.5 J
Let’s convert the speed to m/s. 1
1 mile = 5280 ft/mi * 12 in/ft * 2.54 cm/in * 0.01 m/cm = 1609.344 meters
1 hour = 3600 seconds
1 mi/h = 1609.344/3600 = 0.44704 m/s
This is usually rounded to 0.447 m/s
Speed = 18.8 * 0.447 = 8.4036 m/s
Initial KE = ½ * 88.8 * 8.4036^2
The amount of energy is approximately 3135.5 J