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Q.3. (a) Define friction and state laws of static friction and dynamic friction.
(6)
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b) A uniform ladder of 4 m length rests against a vertical wall with which it (6)
makes an angle of 45°. The coefficient of friction between the ladder and
the wall is 0.4 and that between ladder and the floor is 0.5. If a man,
whose weight is one-half of that of the ladder, ascends it, how high will it
be when the ladder slips?
Q.4. (a) Motion of a particle along a straight line is given by the equation:
(4)
x = t3 - 3t2 - 9 t + 12
Determine the time, position and acceleration of the particle when its
velocity becomes zero.
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b) The distance between two stations A and B is 3.9 km. A train starts from (8)
station A and reach its speed 30 kmph in 20 seconds and travels until the
speed reaches 36 kmph. This speed is maintained until brakes are
applied and the train is brought to rest at the second station B under the
retardation of 0.9 m/s2. Find the time taken to perform this journey.
Q.5. Solve any two:
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(
a) State and explain in brief D’Alembert’s principle.
(6)
b) A motorist is traveling on a curved road of radius 200 m at a speed of 72 (6)
kmph. Find the normal and tangential components of acceleration.
(
c) Boat A is moving north-west at a speed of 36 km/h and the boat B is (6)
moving east at speed 18 km/h. Find the magnitude and direction of the
relative velocity of the boat B with respect to the boat A.
Q.6. Solve any two:
(
(
a) State: The work-energy principle for a system of particles.
(6)
b) A man of mass 60 kg dives vertically downwards into a swimming pool (6)
from a tower of height 20 m. He was found to go down in water by 2 m
and then started rising. Neglect the air resistance. Find the average
resistance of the water.
(
c) An army truck of mass 5 tonnes (t) has tractive resistance of 150 N/t. (6)
Find the power required to propel the truck at a uniform speed of 36
km.p.h. (a) up an incline of 1 in 100 ; (b) on a level track ; and (c) down an
incline of 1 in 100.
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