1. Motion of the tip of second hand of the clock is an example for ___________
a) Uniform circular motion
b) Projectile motion
c) Motion in a plane with uniform velocity
d) Motion in a plane with constant acceleration
Explanation: If a particle moves along a circular path with a constant speed then its motion is said to be a uniform circular motion. Hence, the motion of the tip of the second hand of a clock is an example for uniform circular motion.
2. M0 L0 T(-1) is an example for ___________
a) Angular displacement
b) Angular velocity
c) Frequency
d) Time period
Explanation: The rate of change of angular displacement is called angular velocity. It is measured in radian per second and its dimensional formula is M0 L0 T(-1).
3. A circular motion is an accelerated motion.
a) True
b) False
Explanation: In a uniform circular motion, the direction of the velocity vector which acts along the tangent to the path, remains constant. So circular motion is an accelerated motion.
4. In projectile motion, magnitude remains constant but the direction continuously changes.
a) True
b) False
Explanation: In projectile motion, both magnitude and direction of acceleration remain constant, while in a uniform circular motion the magnitude remains constant but the direction continuously changes.
5. Calculate the angular speed of flywheel making 420 revolutions per minute.
a) 42300 rad/sec
b) 1200 rad/sec
c) 10/4200 rad/sec
d) 44 rad/sec
Explanation: v = 420/60 revolution/ second
ω = 2πv = 2 × 22/7 × 420/60 = 44rad/sec.
6. Find the magnitude of the centripetal acceleration of a particle on the tip of a fan blade, 0.30 metre in diameter, rotation at 1200 rev/minute
a) 40 m/s2
b) 4737.6 m/s2
c) 245 m/s2
d) 20 m/s2
Explanation: v = 1200/60 = 20rps
ω = 2πv = 2×π×20 = 40π rad/sec
Magnitude of acceleration = rω2 = 0.30×(40π)2 = 4737.6 m/s2.
7. Pressure is a vector.
a) True
b) False
Explanation: Pressure is always taken to be normal to the plane of the area on which it is acting. As this direction is unique, it does not need any specification. So the pressure is not a vector.
8. What is the minimum number of coplanar vectors of different magnitudes which can give zero resultant?
a) One
b) Two
c) Three
d) Four
Explanation: If three vectors can be represented by the three sides of a triangle taken in the same order, then their resultant is a zero vector.
9. Two persons are pulling the ends of a string in such a way that the string is stretched horizontally. When a weight of 10kg is suspended in the middle of the string the string does not remain horizontal. Can the persons make it horizontal again by pulling it with a greater force?
a) Yes
b) No
Explanation: The persons cannot make it horizontal again by pulling it with a greater force because the vertical weight cannot be balanced by the horizontal force, however, large the two forces may be.
10. Force is a polar vector.
a) True
b) False
Explanation: Force is a polar vector because it has a point of application. It is a push or a pull that tends to change the state of rest or of uniform motion of a body.