37 (a) (4)
(c) (2)
(d) (3)
(Mains 2010)
(1) Centre of gravity (C. G) of a body is the
point at which the weight of the body acts
(2) Centre of mass coincides with the centre of
gravity if the earth is assumed to have infinitely
large radius.
(3) To evaluate the gravitational field intensity
due to any body at an external point, the entire
mass of the body can be considered to be
concentrated at its C. G
(4) The radius of gyration of any body
rotating about an axis is the length of the
perpendicular dropped from the C. G. of the
body to the axis.
Which one of the following pairs of
statements is correct?
(a) (4) and (1)
(b) (1) and (2)
(c). (2) and (3)
(d) (3) and (4)
(Mains 2010)
The figure shows elliptical orbit of a planet m
about the sun S. The shaded area SCD is twice
the shaded area SAB. If t, is the time for the​

A23 kg log of wood begins from rest, 300 m up a sluice (a water track used to transport logs, think of it as an inclined plane with negligible friction) inclined at 20° to the horizontal. after it reaches the flat waterway at the bottom it collides elastically with a 100 kg block of wood initially at rest near the base of the incline. (a) how long does it take the 23 kg log to travel down the incline? (b) what is the speed of the 23 kg log at the bottom of the incline? (c) what are the velocities of both blocks of wood after the collision? (d) what is the total kinetic energy before the collision? (e) what is the kinetic energy of the 23 kg log after the collision? (f) what is the kinetic energy of the 100 kg block of wood after the collision? (g) what is the total kinetic energy after the collision? (h) compare the total initial and total final kinetic energies. is this consistent with what you would expect for elastic collisions? explain!

An important dimensionless parameter concerned with very high-speed flow is the mach number, defined as v/c, where v is the speed of the object such as an airplane or projectile, and c is the speed of sound in the fluid surrounding the object. for a projectile traveling at 1170 mph through air at 50 ˚f and standard atmospheric pressure, what is the value of the mach number?

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.