MCQs
- A body is moving in a circular path of radius ‘r’, then, displacement and distance travelled by body when angular displacement is 90o is
- r and [latex]\sqrt{2}r[/latex]
- [latex]\sqrt{2}r[/latex] and [latex]\frac{\pi r}{4}[/latex]
- 2r and [latex]\pi r[/latex]
- none
CONCEPTUAL PROBLEMS
- From a flying aeroplane a body should be dropped in advance to hit the target, why?
- A ball is dropped gently from the top of a tower and another ball is thrown horizontally at the same time. Which ball will hit the ground first?
- Can an object with constant acceleration reverse its direction? Explain.
- Velocities of two bodies A and B are given in vector notation as and respectively. What will be the relative velocity of B with respect to A in this notation? Ans:
5. Two stones P and Q of different masses m and 2m respectively are dropped simultaneously from the top of a tower and reach the ground with different energies. Which one is faster?
6. From a high tower, one ball is dropped from rest and the second ball is simultaneously projected horizontally. Neglecting air resistance, which ball will reach the ground earlier?
7. A ball is thrown with a velocity v at an angle with the horizontal. Can another angle of projection achieve the same horizontal range? Justify your answer.
8. Rain drops hitting the side windows of a car, in motion often leave diagonal streaks. Why?
9. If the displacement of body is proportional to square of time, state whether the body is moving with uniform velocity or uniform acceleration.
10. A bomb is to be dropped from a moving helicopter on a target on the ground. Explain how it can hit the target.
11. Can you have a zero acceleration but non-zero velocity? Explain with help of a graph.
12. A projectile move in a parabolic path without air resistance. Is there any point at which its acceleration is perpendicular to the velocity? Explain.
13. Angle between the velocities and of two bodies A and B is . Explain, with figure, the difference between the relative velocity of
(i) A with respect to B and (ii) B with respect to A.
14. Can the direction of the velocity of a body be changed when its acceleration is constant?
15. Can a body have a constant spaced but changing velocity? Explain with example.
16. When a rifle is fired at a distant target, the barrel is not lined up exactly on the target. Why not? Does the angle of projection depend on the distance of the target?
17. A swimmer wants to reach to a point just opposite on the other bank of the river. How should he swim and why?
18. A package is dropped out of an aeroplane in a level flight. If air resistance is neglected, how would the motion of the package look to the pilot?
19. A body is thrown vertically upwards from the ground with a velocity v. It reaches the maximum height and returns to the ground. The same body is projected with the same velocity but making an angle 30° with the horizontal. In which case the body remains in air for longer duration? Explain.
20. A motor cycle is moving with v towards east and crosses a bicyclist coming with a velocity v from north-east direction. How will you find the relative velocity of motor cycle with respect to the bicyclist?
21. Find the angle of projection at which the horizontal range and maximum height of a projectile are equal.
22. What would be the effect on maximum range in doubling the initial velocity of a projectile?
23. Can an object have an eastward velocity experiencing a westward acceleration? Give reasons.
24. A car is moving on the road when the rain is falling vertically downwards. Why does the front wind screen get wet?
25. A projectile fired at an angle of 18° has certain horizontal range. State another angle of projection for the same horizontal range.
26. Give with an example a case where the velocity of an object is zero but its acceleration is not zero. 27. Because of air resistance two objects of unequal mass do not fall at precisely the same rate. If two bodies of identical shape but unequal mass are dropped simultaneously from the same height, which one reaches the ground first?