the child pushing the toy car across the carpet. Toward the end of the scenario,
ID: 1573390 • Letter: T
Question
the child pushing the toy car across the carpet. Toward the end of the scenario, while still in contact with both the hand and the carpet, the toy car decreased in speed and stopped. Note that during this period the car and the carpet continued to get warmer because friction was still affecting them.
1.While the speed of the toy car was decreasing, what can you say about the tendency of the two interactions involved?
A. the tendency of interaction with the hand to increase the kinetic energy of the cart was STRONGER than the tendency of the interaction with the carpet to decrease its kinetic energy.
B. the tendency of interaction with the hand to increase the kinetic energy of the cart was EQUAL TO the tendency of the interaction with the carpet to decrease its kinetic energy.
C. the tendency of interaction with the hand to increase the kinetic energy of the cart was WEAKER than the tendency of the interaction with the carpet to decrease its kinetic energy.
2.During this situation what type of state was the car in with respect to its kinetic energy?
A. transient B. equilibrium C. neither or these
3. Which of the following would be an appropriate statement of conservation of energy for this situation? (CPE = chemical potential energy, EPE = elastic potential energy, KE = kinetic energy)
Explanation / Answer
Here
1.
though the hand is still in contact with toy car but the car decreased in speed and come to rest because of the friction by the carpet to the toy car
that is
the tendency of interaction with the hand to increase the kinetic energy of the cart was WEAKER than the tendency of the interaction with the carpet to decrease its kinetic energy.
2. the sate of the car is neither Transient nor in equilibrium
if the state of the car is transient then it may not come to rest
or if the state of the car is equilibrium it does not make any displacement
3. the conservation of energy is kinetic energy only
the equivalent energy is converted in to heat due to friction
so
1.c
2. C
3. KE
equation is change in k.e = work done by the friction about the displacement x
0.5*m*(v2^2-v1^2) = F_f*s cos theta
here the angle theta =0 (straight line path)
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