A pulley of radius 2m is rotated about its axis by a force F = (20t - 5t2) Newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg-m2, the number of rotations made by the pulley before its direction of motion if reversed is
more than 3 but less than 6
more than 6 but less than 9
more than 9
more than 9
A.
more than 3 but less than 6
To reverse the direction
A liquid in a beaker has temperature θ(t) at time t and θ0 is temperature of surroundings, then according to Newton's law of cooling the correct graph between loge (θ – θ0) and t is
A.
According to Newton's law of cooling.
Hence the plot of ln(θ – θ0) vs t should be a straight line with negative slope.
Work done in increasing the size of a soap bubble from a radius of 3 cm to 5 cm is nearly. (Surface tension of soap solution = 0.03 Nm-1)
4π mJ
0.2π mJ
2π mJ
2π mJ
D.
2π mJ
Work done = Change in surface energy
⇒ W = 2T x 4π (R22-R12)
= 2 x 0.03 x 4π [ (5)2-(3)2] x 10-4 J
= 0.4 π mJ
STATEMENT – 1
Two particles moving in the same direction do not lose all their energy in a completely inelastic collision.
STATEMENT – 2
Principle of conservation of momentum holds true for all kinds of collisions.
The statement I is True, Statement II is False.
The statement I is True, Statement II is True; Statement II is a correct explanation for Statement I.
The statement I is True, Statement II is True; Statement II is not the correct explanation for Statement I.
The statement I is True, Statement II is True; Statement II is not the correct explanation for Statement I.
B.
The statement I is True, Statement II is True; Statement II is a correct explanation for Statement I.
A mass m hangs with the help of a string wrapped around a pulley on a frictionless bearing. The pulley has mass m and radius R.Assuming pulley to be a perfect uniform circular disc, the acceleration of the mass m, if the string does not slip on the pulley, is
g
2/3g
g/3
g/3
B.
2/3g
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