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#### Motion of System of Particles and Rigid Bodies Two Marks Question

11th Standard

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Physics

Time : 00:45:00 Hrs
Total Marks : 30
15 x 2 = 30
1. What is point mass?

2. State the rule which is used to find the direction of torque.

3. State the torque about an axis is independent of the origin.

4. State law of Conservation of angular momentum.

5. When a tree is cut, the cut is made on the side facing the direction in which the tree is required to fall. Why?

6. Why does a porter bend forward while carrying a sack of rice on his back?

7. Give an example to show that the following statement is false. 'any two forces acting on a body can be combined into single force that would have same effect'.

8. A rectangle block rests on a horizontal table. A horizontal force is applied on the block at a height h above the table to move the block. Does the line of action of the normal force N exerted by the table on the block depend on h?

9. Four bodies of masses 5 kg, 2 kg, 3 kg and 4 kg are respectively placed at position (0, 0, 0), (2, 0, 0) (0, 3, 0) and (-2, -2, 0) calculate the moment of inertia about x-axls, y-axis and z-axis.

10. Give examples where the centre of mass coincides with the geometrical centre of the body.

11. The distance between the centres of carbon and oxygen atoms in the carbon monoxide gas molecule is 1.13 $\mathring{A}$ . Locate the centre of mass of the gas molecule relative to the carbon atom.

12. What is a rigid body?

13. When an object will have precession? Give one example.

14. An electron of mass 9 x 10-31 kg revolves around a nucleus in a circular orbit of radius 0.53 $\overset { 0}{ A }$. What is the angular momentum of the electron? (Velocity of electron is, v = 2.2 x 106 ms-1)

15. A solid sphere of mass 20 kg and radius 0.25 m rotates about an axis passing through the center. What is the angular momentum if the angular velocity is 5 rad s-1.