21.

A solid sphere and a hollow sphere are heated the same temperature. Point out the true statement.

• hollow sphere cools more quickly

• both hollow and solid sphere cools more quickly

• solid sphere cools more quickly

• none of the statement is true

The time period of a simple pendulum is T remaining at rest inside a lift. Find the time period of pendulum when lift starts to move up with an acceleration of  g/4

• T

• T/2

• $\frac{2\mathrm{T}}{5}$

• $\frac{2\mathrm{T}}{\sqrt{5}}$

1 Kcal of heat flowing through a rod iron. When the rod is cut down to 4 pieces then what will be the heat flowing through each piece having same differential temperature?

• 1/2 Kcal

• 1/4 Kcal

• 1 Kcal

• 1/15 Kcal

From the given figure find the  frequency of oscillation of the mass m. 

If fundamental frequency is 50 and next successive frequencies are 150 and 250 then it is

• a pipe closed at both end

• a pipe closed at one end

• an open pipe

• a stretched pipe

Temperature of the star is determined by

• distance

• colour

• size

• none of these

If hot water is mixed with cold water

• temperature first increases then become constant

• temperature first decreases then become constant

• increases continuously

• first it is uncertain then it become constant

For liquid to rise in a capillary tube, the angle of contact should be

• acute

• obtuse

• right

• none of these

The heat produced in a long wire is characterized by resistance, current and time through which the current passes. If the errors in measuring these quantities are respectively 1 %, 2% and 1%, then the total error in calculating the energy produced is

• 4%

• 6%

• 4/3 %

• 8%

Anatomy and Bismuth are usually used in thermocouple, because

• a constant e..m.f is produced

• higher thermo e.m.f is produced

• a negative e.m.f is produced

• lower thermo e.m.f is produced