A cylindrical steel rod of length 0.10 m and thermal conductivity 50 W.m–1 K–1 is welded end to end to copper
rod of thermal conductivity 400 W.m–1. K–1 and of the same area of cross section but 0.20 m long. The free end of
the steel rod is maintained at 100º C and that of the copper and at 0º C. Assuming that the rods are perfectly
insulated from the surrounding, the temperature at the junction of the two rods
A ball of mass m suspended from a rigid support by an inextensible massless string is released from a height h
above its lowest point. At its lowest point it collides elastically with a block of mass 2m at rest on a frictionless
surface. Neglect the dimensions of the ball and the block. After the collision the ball rises to a maximum height
of–
The potential energy of a point particle is given by the expression V (x) = –αx + β sin (x/γ). A dimensionless
combination of the constant α, β and γ is
Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is
held at a temperature of 100ºC while the other one is kept 0º C. If the two are brought into contact, then, assuming
no heat loss to the environment, the final temperature that they will reach is
A body is executing simple harmonic motion of amplitude a and period T about the equilibrium position x = 0.
large numbers of snapshots are taken at random of this body in motion. The probability of the body being found in
a very small interval x to x + |dx| is highest at
A steady current I flows through a wire of radius r, length L and resistivity ρ. The current produced heat in the
wire. The rate of heat loss in a wire is proportional to its surface area. The steady temperature of the wire is
independent of–
(A) L (B) r (C) I (D) ρ
A loop carrying current I has the shape of a regular polygon of n sides. If R is the distance from the centre to any
vertex, then the magnitude of the magnetic induction vector B
at the centre of the loop is
Seven identical coins are rigidly arranged on a flat table in the pattern shown below so that each coin touches its
neighbors. Each coin is a thin disc of mass m and radius r. Note that the moment of inertia of an individual coin
about an axis passing through centre and perpendicular to the plane of the coin is mr2 / 2
The moment of inertia of the system of seven coins about an axis that passes through the point P (the centre of the
coin positioned directly to the right of the central coin) and perpendicular to the plane of the coins is–