Question

You wish to lift a
heavy block through
a height h by
attaching a string of
negligible mass to it and pulling so that it moves at
a constant velocity. You have the choice of lifting it
either by pulling the string (i) vertically upward or
(ii) along a frictionless inclined plane (see
diagram). Which one of the following statements is
true?
(a) The magnitude of the tension force in the string
is smaller in case (i) than in case (ii).
(b) The work done on the block by the tension force
is the same in both cases.
(C) the work done on the block by the tension force is smaller in case (ii) Than in case (i)
(d) the work done on the block by the gravitational force is smaller in case (ii) than in case (i)

Answer 1

Answer:

the option is D the work done by the block by gravitational force is smaller

Answer 2

The true statement is : (c) The work done on the block by tension force is smaller in case (ii) than in case (i)

The tension in the rope in the first case , T₁ = mg [ m = mass of the object]

The tension in the rope in the second case,  T₂ = mg Sin θ

Where θ is the angle at which the plain is inclined.

θ is acute, and Sinθ is increasing between 0 to +1, so   T₁ > T₂

So, (a) is not true.

Work done can not be same, as tensions are different.

So, (b) is not true.

As, T₁ > T₂, so the work done on the block by the tension in the second case will be smaller than the work done in the second case.

So, (c) is the correct answer.