7. An elevator desoends at a constant velocity. Which of the following is true?

Question

7. An elevator desoends at a constant velocity. Which of the following is true? a. The total energy of the elevator is not conserved because a non-conservative force does work on the elevator b. The total energy of the elevator is conserved because no ret external force acts on the elevator. c. The total energy of the elevator is conserved because energy is always conserved d. The total energy of the elevator is not conserved because a net external force acts on the elevator. 8 Mechanical energy of a system is conserved whern

Explanation / Answer

Q7

If velocity is constant .so kinetic energy is constant

but potential energy will decrease as it is descending

so correct answer is

option (d)

Q14

a=gsin(theta)-0.25*g*cos(theta)=3.92 m/s^2

time taken=sqrt(2*5/a)=1.59 sec=1.6sec

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