## Statics Very Short Answer Type Questions

**Question 1. A rocket in space is being propelled by the ejection of a gas. What is the velocity of the centre of mass of the rocket-fuel system?**

**Answer:** Zero

**Question 2. A rocket in space is being propelled by the ejection of a gas. Will the velocity of the centre of mass of the rocket be zero?**

**Answer:** No

**Question 3. Can the centre of mass of a body lie outside the body?**

**Answer:** Yes

**Question 4. Does the centre of mass of a body necessarily lie inside the body?**

**Answer:** May lie outside the body example, the CM of a circular ring is at the centre of the circle which is outside the ring.

**Question 5. Give the location of the centre of mass of a solid cylinder having uniform mass density.**

**Answer:** At the mid-point of the straight line joining the two centres of the circular end faces

**Question 6. Two particles, due to their mutual attraction, approach each other. Give the value of the velocity of the centre of mass of the system at the moment when their relative velocity is v.**

**Answer:** Zero

**Question 7. A uniform rod of length 1 m is bent at right angles at its mid-point. What is the distance of the centre of mass from the mid-point of the rod?**

**Answer:** 17.7 cm

**Question 8. Write down the CGS unit of the moment of force.**

**Answer:** dyn cm

**Question 9. Write down the dimension of the moment of force.**

**Answer:** ML^{2}T^{-2}

**Question 10. Write down the name of the anticlockwise moment of a force.**

**Answer:** Positive moment

**Question 11. Mention the clockwise moment of a force.**

**Answer:** Neganve moment

**Question 12. The moment of a force about a point is ______ the area of the triangle formed by joining that point, the initial point of application of the force and the final point of application of the force.**

**Answer:** Double

**Question 13. ‘Moment of force is a vector’—true or false?**

**Answer:** True

**Question 14. Give the vector representation of the moment of force.**

**Answer:** \(\vec{G}=\vec{r} \times \vec{F}\)

**Question 15. It is _____ to open a door by pushing it near the outer edge rather than by pushing it near the hinge.**

**Answer:** Easier

**Question 16. Some forces act at a point such that their magnitudes and directions can be represented by the sides of a closed polygon taken in order. What is the resultant of the forces?**

**Answer:** Zero

**Question 17. Lengths of the arms of a balance are equal but the weights of the pans are different. When an object is put on the left pan, it weighs W _{1} and on the right pan, it weighs W_{2}. What is the actual weight of the object?**

**Answer:**\(\left[\frac{w_1+w_2}{2}\right]\)

**Question 18. A man is at the top of a ladder and in another instance he stands on one of the lower steps. In which case does the foot of the ladder have a higher chance of slipping?**

**Answer:** The man at the top of the ladder

**Question 19. Can two unequal forces that lie in the same plane produce equilibrium?**

**Answer:** No

**Question 20. ‘A gas-filled balloon remains at rest at a certain height. The balloon is in stable equilibrium’—correct or incorrect?**

**Answer: ** Correct

**Question 21. ‘When a body revolves in a circular path at a constant speed, it is in an unstable equilibrium’—true or false?**

**Answer:** True

**Question 22. At one end of a weightless rope of length 10 m, a car of mass M is tied. The other end of the rope is in the hands of a man of mass M. The arrangement stands on a horizontal frictionless surface. The man is at x = 0 and the car is at x = 10 m. As the man pulls the car with the rope, locate the point where they meet.**

**Answer:** x = 5m

**Question 23. Under the action of three forces F, F and √2F, a particle remains in equilibrium. Find the angle between the first two forces.**

**Answer:** 90

**Question 24. What is the position of the centre of gravity of a uniform rectangular lamina?**

**Answer:** At the point of intersection of the diagonals

**Question 25. For a uniform body, if the shape is kept the same but its size is changed uniformly, will the position of the centre of gravity change?**

**Answer:** No

**Question 26. When a uniform rod is heated at one of its ends, will the position of the centre of gravity be shifted?**

**Answer:** Yes

**Question 27. Does the centre of gravity change it’s position if the shape changes of a body without a change of its weight? **

**Answer:** Yes

**Question 28. Is the centre of gravity of a body to be many?**

**Answer:** No

**Question 29. Can the centre of gravity of a long glass tube lie at the midpoint of its length?**

**Answer:** Yes

**Question 30. A rod weighing W is placed horizontally over knife edges A and B. The Distance between the knife edges is d and the distance of the centre of gravity of the rod from**

**A is x. What are the reactions at A and B?**

**Answer:** \(\left[W\left(1-\frac{x}{d}\right), W \frac{x}{d}\right]\)

**Question 31. ‘Centre of mass and centre of gravity of a body are not the same, in general’—correct or incorrect?**

**Answer:** Correct