3 multiple choice question : ( can you also explain why ) 1.An object of mass m

Question

3 multiple choice question : ( can you also explain why )

1.An object of mass m is hung from the lower end of a vertical rope of negligible mass. What is the tension in the rope if the object has a downward acceleration a on the surface of the Earth?

(a) m(g - a) (b) g + a (c) ma (d) g-a (e) m(g + a)

2.The power required to keep a particular car moving at a constant speed v against drag at low speeds is P. What is the power required to move the car at 2v?

(a) P (b) 2P (c) 4P (d) 8P (e) none of [a-d]

3.A spring under a compression x has a potential energy Vo. When the compression is doubled 2x, the potential energy stored in the spring is

(a) Vo (b) 2Vo (c) 3Vo (d) 8Vo (e) None of [a-d] is correct.

Explanation / Answer

1) equation of motion of the object

ma= F

ma=mg-T

T= m(g-a)

b) power =force x velocity

power is proportional to velocity

ans :- 2P

3) p.e. =(1/2)k*x^2

V0=(1/2)k*x^2

(1/2)k*(2x)^2=4V0

option e

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