Select the correct answers of the following questions:
- The angular speed in rad/hours for daily rotation of our earth is
2π | 4π | π/6 | π/12 |
Solution
In the complete rotation, the earth traverses an angle = 2π rad
Time taken in a complete rotation = 24 hrs Therefore, angular speed
2. Linear acceleration is a = rα when θ is
0^{o} | 180^{o} | 360^{o} | 90^{o} |
Explanation: Relation of linear and angular acceleration is
Its magnitude is rasinα. For α = 90° sin90° = 1, therefore, a = rα.3. What is moment of inertia of a sphere
MR^{2} | ½ MR^{2} | 2/5 MR^{2} | ½ M^{2}R |
4. Artificial satellite moves around
Moon | Sun | Star | Earth |
5. A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle. The motion of the particle takes place in a horizontal plane. It follows
Linear momentum is constant | Velocity is constant | It moves in a circular path | None of these |
6. A body moving along a circular path with constant speed has
Constant acceleration | Constant retardation | Variable acceleration | Variable speed and constant acceleration |
Explanation: When a body is moving in circular path, its direction changes at every point. Since change in direction is accompanied by a change in the acceleration on every point, therefore, the body moving in a circle has variable acceleration.
7. Which one is constant for a satellite in the orbit?
Velocity | K.E | Angular Momentum | P.E |
Explanation: Since angular momentum, L = r x p.
A satellite has constant mass and speed, therefore, its linear momentum p is constant. Similarly, the radius r is also constant. Therefore, angular momentum L is constant.
8. If earth suddenly stops rotating the value of ‘g’ at equator would
Decreases | Remains constant | Increases | Becomes zero |
Explanation: When the earth stops its rotation about its own axis, the centrifugal force is also stopped. This increases the gravitational force. (Note that the centrifugal force is more on equator than the poles).
9. If a solid sphere and cylinder of mass and density rotate about their own axis, the moment of inertia will be greater for
Solid sphere | Solid cylinder | Both | Equal both |