The minimum force required to start pushing a body up a rough (frictional coefficient μ) inclined plane F1 while the minimum force needed to prevent it from sliding down is F2. If the inclined plane makes an angle θ from the horizontal such that tan θ= 2μ then the ratio F1/F2 is
(a) 4
(b) 1
(c) 2
(d) 3
The upper half of an inclined plane with inclination Φ is perfectly smooth, while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom, if the coefficient of friction for the lower half is given by
(a) 2 sinΦ
(b) 2 cosΦ
(c) 2 tanΦ
(d) tanΦ
A block rests on a rough inclined plane making an angle of 300 with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 N, the mass of the block (in kg) is : (taken g =10 m/s2)
(a) 2.0
(b) 4.0
(c) 1.6
(d) 2.5
A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is 0.2. The weight of the block is-
(a) 20 N
(b) 50 N
(c) 100 N
(d) 2 N
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
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