Open Question
(I) You drop a basketball from a height of 5.0 m, which rebounds to a new height of 3.0 m. How much energy is lost to nonconservative forces? Give your answer as percentage of the initial energy.
10. Conservation of Energy
Energy with Non-Conservative Forces
Multiple Choice
An 800kg car skids to a stop from 30m/s through a distance of 90m. Calculate the coefficient of friction between the car and the road.
A
0.51
B
1.23
C
0.73
D
0.02
Verified step by step guidance1
Identify the forces acting on the car. The car is subject to gravitational force and frictional force. The frictional force is what causes the car to stop.
Use the work-energy principle which states that the work done by friction is equal to the change in kinetic energy of the car. The initial kinetic energy can be calculated using the formula: , where is the mass of the car and is its initial velocity.
Calculate the work done by friction using the formula: , where is the frictional force and is the distance over which the car skids.
Relate the frictional force to the normal force using the coefficient of friction: , where is the coefficient of friction and is the normal force, which is equal to the weight of the car: .
Set up the equation from the work-energy principle: . Solve for to find the coefficient of friction.
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