Q72 of 146 Page 148

The work done by a force acting obliquely is given by the formula: W = F Cos θ × s. What will happen to the work done if angle between the direction of force and motion of the body is increased gradually? Will it increase, decrease or remain constant?

On increasing the value of angle between force and distance, the value of Cos θ decreases to zero when θ=90∘.Therefore, work done decrease as angle increase, work done is 0 when θ = 90∘ and work done is negative when angle further increases.

Cos θ reduces further to –1.


Therefore, work done decrease as angle increase, work done is 0 when θ=90∘ and work done is negative when angle further increases.


More from this chapter

All 146 →
70

A stone is thrown upwards as shown in the diagram. When it reaches P, which of the following has the greatest value for the stone?

A. Its acceleration


B. Its kinetic energy


C. Its potential energy


D. Its weight

 71

A boy tries to push a truck parked on the roadside. The truck does not move at all. Another boy pushes a bicycle. The bicycle moves through a certain distance. In which case was the work done more: on the truck or on the bicycle? Give a reason to support your answer.

 73

What should be the angle between the direction of force and the direction of motion of a body so that the work done is zero?

 74

In which of the following case the work done by a force will be maximum: when the angle between the direction of force and direction of motion is 0o or 90o?