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A reference frame attached to the earth

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Important Questions on Laws of Motion

EASY
A block A takes 2 s to slide down a frictionless incline of 30° and length l, kept inside a lift going up with uniform velocity v. If the incline is changed to 45°, the time taken by the block, to slide down the incline, will be approximately:
HARD

Two wooden blocks are moving on a smooth horizontal surface such that the block having mass m remains stationary with respect to block of mass M as shown in the figure below. The magnitude of the applied force P is, 

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EASY
A block of mass M placed inside a box descends vertically with acceleration a. The block exerts a force equal to one-fourth of its weight on the floor of the box. The value of a will be
EASY
A person is standing in an elevator. In which situation, he experiences weight loss ?
MEDIUM
A boy is standing on a weighing machine inside a lift. When the lift goes upwards with acceleration g4, the machine shows the reading 50kg. wt. When the lift goes downward with acceleration g4, the reading of the machine in kg. wt. would be
EASY
A man weighing 60 kg is in a lift moving down with an acceleration of 1.8 ms-2. The force exerted by the floor on him is?
MEDIUM
When a lift of mass 800 kg is ascending with an acceleration of 5 m s-2, the tension in its cable will be ______ take (g=10 m s-2
MEDIUM
A rocket is fired vertically from the earth with an acceleration of 2g, where g is the gravitational acceleration. On an inclined plane inside the rocket, making an angle θ with the horizontal, a point object of mass m is kept. The minimum coefficient of friction μmin between the mass and the inclined surface such that the mass does not move is:
HARD
A girl drops an apple from the window of a train which is moving on a straight track with speed increasing with a constant rate. The trajectory of the falling apple as seen by the girl is
EASY
A plumb line is suspended from a ceiling of a car moving with horizontal acceleration a. What will be the angle of inclination with vertical?
MEDIUM
Two blocks  A and  B of masses mA=1 kg and mB=3 kg are kept on the table as shown in figure. The coefficients of friction between A and B is 0.2 and between  B and the surface of the table is also 0.2. The maximum force F that can be applied on B horizontally, so that the block  A does not slide over the block B is : [Take  g=10 m/s2 ]
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HARD
A particle is moving along the x -axis with its coordinate with time t given by xt=10+8t-3t2. Another particle is moving along the y -axis with its coordinate as a function of time given by yt=5-8t3. At t=1 s, the speed of the second particle as measured in the frame of the first particle is given as v. Then vin m s-1 is ___________.
EASY
Assertion: A body whatever its motion is always at rest in reference frame which is fixed to the body itself.

Reason: The relative velocity of a body with respect to itself is always zero.
MEDIUM
A bird is sitting in a large closed cage which is placed on a spring balance. It records a weight of 5N. The bird of mass 0.5 kg files upward in the cage with an acceleration of 2 ms-2. The spring balance will now record a weight of......... at that moment?
MEDIUM
Assertion: An observer moving with constant speed must be an inertial reference frame.

Reason: An observer is called inertial if its change in velocity is zero.
EASY
Assertion: Inertia is the property by virtue of which the body is unable to change by itself the state of rest only.

Reason: The bodies do not change their state unless acted upon by an unbalanced external force.
EASY
Statement 1 :  A particle is found to be at rest when seen from a frame S1 and moving with a constant velocity when seen from another frame S2. We can say both the frames are inertial.

Statement 2 :  All frames moving uniformly with respect to an inertial frame are themselves inertial.
EASY
An intersteller spacecraft far away from the influence of any stars or planets is moving at high speed under the influence of fusion rockets (due to thrust exerted by fusion rockets the spacecraft is accelerating). Suddenly the engine malfunction and stops. The spacecraft will
EASY
Which of the following statements is not true about reference frames (NEGLECT ANY EFFECT OF RELATIVISTIC MECHANICS).