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21. The speed of an object falling freely is an example of ________.
A. Rectangular motion
B. Uneven accelerated motion
C. Uniform acceleration motion
D. Circular motion
ANSWER:C
SOLUTION :The speed of an object falling freely is an example of uniformly accelerated motion. Uniform acceleration is a type of motion where an object’s velocity changes by an equal amount in every equal time period. In the case of a freely falling object, gravity causes acceleration, which is uniform because gravity is almost uniform in the atmosphere.
22. When bullet is fired from the gun, the gun pushes in the opposite direction. This is an example of Newton’s law ________.
A. First and second laws of motion
B. Third law of motion
C. Second law of motion
D. First law of motion
ANSWER:B
SOLUTION:According to Newton’s Third Law of motion, every action has an equal and opposite reaction. When a gun fires a bullet, the gun puts a force on the bullet that propels it forward. The bullet likewise exerts an equal and opposing force on the gun in the backward direction.
23. Which of the following examples illustrates Newton’s first law of motion ?
A. When we stop pedaling, the cycle starts to slow down
B. While catching a fast approaching cricket ball, the fielder slowly moves his hand backwards with the moving ball
C. When a bus starts abruptly, the passengers are jerked backwards
D. Rocket launching
ANSWER:C
SOLUTION:When a bus starts abruptly, the passengers are jerked backwards.
24. If we move the tree branch fast then some of the leaves get detached from the tree due to _______.
A. Acceleration
B. Velocity
C. Inertia
D. Impulse
ANSWER:C
SOLUTION:Leaves of tree may get detached from a tree, if we vigorously shake its branch due to inertia of rest. Leaves are in the state of rest with respect to the tree so they possess inertia of rest.
25. Among which of the following is the maximum value of inertia?
A. Same size of rubber ball and stone
B. Scooter and bus
C. Ten rupee coins and five rupee coins
D. Trains and aeroplanes
ANSWER:D
SOLUTION:Inertia is the tendency of undisturbed objects to remain at rest or to continue moving at the same speed. The quantity of mass in a body determines its inertia. A body of larger mass has more inertia; hence Trains and Airplanes has more inertia than the other examples given.
26. Speed of body is _______.
A. The distance covered by a moving body in unit time
B. Always equal to velocity of body
C. A vector quantity
D. None of the above
ANSWER:A
SOLUTION : The speed of a body is the distance traveled by it per unit of time. Speed has only magnitude, it has no specific direction. So, it is a scalar quantity.
27. At any moment , the acceleration of a rocket is proportion to the nth power of the velocity of the released gases. The value of ‘n’ should be ____.
A. 1
B. 2
C. -1
D. -2
ANSWER:A
SOLUTION: At an instant, the acceleration of a rocket is proportional to the nth power of the velocity of exhaust gases. The value of n here is 1. If the gases are expelled at velocity v, then the rate of change in linear momentum is equal to mv where m is the mass of the gases.
28. An athelete runs for some time before the high jump so that the inertia of the _____ helps him take the long jump.
A. Rest
B. Direction
C. Size
D. Speed
ANSWER:D
SOLUTION: Speed.
29. The distance- time graph for the motion of an object moving with a constant speed is a _______.
A. Dot
B. Circle
C. Straight line
D. Curve
ANSWER:C
SOLUTION: The distance-time graph of the motion of an object moving with a contant speed is a straight line.
30. A wheel – barrow is an example of ______.
A. Class III lever
B. Pulley system
C. Class I lever
D. Class II lever
ANSWER:D
SOLUTION: A wheel barrow is an example of second class lever as the load is between the fulcrum and effort,hence it is a second class lever.