[1 Mark Question Answer]

Question 11 Mark

Two forces each of magnitude 2 N act vertically upward and downward respectively on two ends of a uniform rod of length 1 m, freely pivoted at its centre. Determine the resultant moment of forces about the mid-point of the rod.

Answer

Given, Force $=2 N ;$ Arm of couple $=1 m=$ Length of the rod
Resultant moment of forces $=$ Moment of couple
$\therefore$ Moment of couple $=$ Force $\times$ Arm of couple $=2 N \times 1 m=2 Nm$.

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Question 21 Mark

Calculate the force which will produce a moment of force of 1575 dyne-cm, when the perpendicular distance between point of application of force and turning point is 45 cm.

Answer

Given, Moment of force $=1575$ dyne-cm; $\perp$ distance $=45 cm$.
$\therefore$ Force $=\frac{\text { moment of force }}{\perp \text { distance }}=\frac{1575 \text { dyne-cm }}{45 cm}=35$ dyne.

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Question 31 Mark

A force of 50 dynes acts on a rigid body, such that the perpendicular distance between the fulcrum and the point of application of force is 75 cm. Calculate the moment of force.

Answer

Given, $F =50$ dynes; $\perp$ Distance $=75 cm$.
$\begin{aligned}\therefore \text { Moment of force } & =F \times \perp \text { distance } \\
& =50 \text { dyne } \times 75 cm=3750 \text { dyne-cm. }\end{aligned}$

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Question 41 Mark

(a) What do you understand by the term center of gravity?
(b) What is the position of the CG for a cylinder?

Answer

(a) Centre of gravity is a point generally within a body where the whole weight of the body is supposed to act.
(b) Position of CG in case of a cylinder is at the centre of its axis.

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Question 51 Mark

With reference to magnitude of force and its direction, how does centripetal force differ from centrifugal force?

Answer

Centripetal force is directed towards the centre of the circular path of a rotating body. Whereas centrifugal force is directed away from the centre along the radius of its circular path. The magnitude of centripetal force is same as that of the centrifugal force.

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Question 61 Mark

Can a body moving with uniform speed, have an accelerated motion? Give an example.

Answer

Yes, a stone tied to a strong thread and whirled around a point at a constant speed moves along a circular path with uniform speed. But as the stone changes its direction constantly, the motion is accelerated. Thus the stone exhibits uniform circular motion.

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Physics [1 Mark Question Answer]

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