Choose the correct alternative :
(a) Acceleration due to gravity increases/decreases with increasing altitude.
(b) Acceleration due to gravity increases/decreases with increasing depth (assume the
earth to be a sphere of uniform density).
(c) Acceleration due to gravity is independent of mass of the earth/mass of the body.
(d) The formula –G Mm(1/r2 – 1/r1) is more/less accurate than the formula
mg(r2 – r1) for the difference of potential energy between two points r2 and r1 distance
away from the centre of the earth.
Answer the following :
(a) You can shield a charge from electrical forces by putting it inside a hollow conductor.
Can you shield a body from the gravitational influence of nearby matter by putting
it inside a hollow sphere or by some other means ?
(b) An astronaut inside a small space ship orbiting around the earth cannot detect
gravity. If the space station orbiting around the earth has a large size, can he hope
to detect gravity ?
(c) If you compare the gravitational force on the earth due to the sun to that due
to the moon, you would find that the Sun’s pull is greater than the moon’s pull.
(you can check this yourself using the data available in the succeeding exercises).
However, the tidal effect of the moon’s pull is greater than the tidal effect of sun.
Why ?
A cord of negligible mass is
wound round the rim of a fly wheel of mass
20 kg and radius 20 cm. A steady pull of
25 N is applied on the cord as shown in
Fig. 6.31. The flywheel is mounted on a
horizontal axle with frictionless bearings.
(a) Compute the angular acceleration of
the wheel.
(b) Find the work done by the pull, when
2m of the cord is unwound.
(c) Find also the kinetic energy of the
wheel at this point. Assume that the
wheel starts from rest.
(d) Compare answers to parts (b) and (c).
The angular speed of a
motor wheel is increased from 1200 rpm to
3120 rpm in 16 seconds. (i) What is its
angular acceleration, assuming the
acceleration to be uniform? (ii) How many
revolutions does the engine make during
this time?
A 3m long ladder weighing
20 kg leans on a frictionless wall. Its feet
rest on the floor 1 m from the wall as shown
in Fig.6.27. Find the reaction forces of the
wall and the floor.
A metal bar 70 cm long and
4.00 kg in mass supported on two knife-
edges placed 10 cm from each end. A 6.00
kg load is suspended at 30 cm from one
end. Find the reactions at the knife-edges.
(Assume the bar to be of uniform cross
section and homogeneous.)
Show that moment of a
couple does not depend on the point about
which you take the moments.
Show that the angular
momentum about any point of a single
particle moving with constant velocity
remains constant throughout the motion
+91 94284 01196 (WhatsApp only)
C-15, Suvidhapark Society, Amitnagar circle, Karelibaug, Vadodara (390018)
© Copyright 2025. Doubtora. All Rights Reserved
