(1) the object is stationary

(2) the force is always perpendicular to its velocity

(3) the force is always perpendicular to its acceleration

(4) the object moves in such a way that the point of application of the force remains fixed

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(2) the force is always perpendicular to its velocity

(3) the force is always perpendicular to its acceleration

(4) the object moves in such a way that the point of application of the force remains fixed

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Answer: (1), (2) and (4)

Work done by a constant force $W= Fd \cos \theta$

(1) If the object is stationery even when the force is applied, $d = 0 \rightarrow W = 0$

(2) If the force is perpendicular to velocity $\rightarrow \theta = 90^\circ \rightarrow W = 0$, as $\cos 90 = 0$

(4) If the object moves in such a way that the point of application remains fixed then this is an example of circular motion, where the angle $\theta$ between force and displacement is $90^\circ \rightarrow W = 0$ (same math as (2))

(3) is not true as acceleration does not convet direction of displacement unlike velocity.

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