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The efficiency of a fuel cell is given by:
A block of mass $M$ is pulled along a horizontal frictionless surface by a rope of mass $m$. If a force $P$ is applied at the free end of the rope, the force exerted by the rope on the block will be:
Two bodies of equal masses revolve in circular orbits of radii R₁ and R₂ with the same period. Their centripetal forces are in the ratio:
A certain quantity of water cools from $70^{\circ}\text{C}$ to $60^{\circ}\text{C}$ in the first $5\text{ minutes}$ and to $54^{\circ}\text{C}$ in the next $5\text{ minutes}$. The temperature of the surroundings will be:
An engine has an efficiency of $\frac{1}{6}$. When the temperature of the sink is reduced by $62^{\circ}\text{C}$, its efficiency is doubled. The temperature of the source is:
Assume that light of wavelength $600 nm$ is coming from a star. The limit of resolution of telescope whose objective has a diameter of $2 m$ is :
A coin, placed on a rotating turn-table slips, when it is placed at a distance of 9 cm from the centre. If the angular velocity of the turn-table is tripled, it will just slip, if its distance from the centre is:
A bucket tied at the end of a 1.6 m long string is whirled in a vertical circle with constant speed. What should be the minimum speed so that the water from the bucket does not spill, when the bucket is at the highest position? (Take $g = 10 \text{ m/s}^2$)
A carnot engine having an efficiency of $\frac{1}{10}$ as a heat engine, is used as a refrigerator. If the work done on the system is $10\text{ J}$, the amount of energy absorbed from the reservoir at lower temperature is:
In thermodynamic processes, which of the following statements is not true?
The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be
A truck and a car are moving with equal velocity. If equal retarding force is applied on each, then on applying the brakes both will stop after certain distance:
A body of mass 0.4 kg is whirled in a vertical circle making 2 rev/sec. If the radius of the circle is 2 m, then tension in the string when the body is at the top of the circle is:
Steam at $100^{\circ}\text{C}$ is passed into $20\text{ g}$ of water at $10^{\circ}\text{C}$. When water acquires a temperature of $80^{\circ}\text{C}$, the mass of water present will be (Take specific heat of water $= 1\text{ cal g}^{-1\circ}\text{C}^{-1}$ and latent heat of steam $= 540\text{ cal g}^{-1}$)
One mole of an ideal monatomic gas undergoes a process described by the equation $PV^3 = \text{constant}$. The heat capacity of the gas during this process is:
When $1 \text{ kg}$ of ice at $0^{\circ}\text{C}$ melts into water at $0^{\circ}\text{C}$, the resulting change in its entropy, taking the latent heat of ice to be $80 \text{ cal/g}$, is:
A machine gun is mounted on a 2000 kg car on a horizontal frictionless surface. At some instant, the gun fires bullets of mass 10 g with a velocity of 500 m/s with respect to the car. The number of bullets fired per second is ten. The average thrust on the system is:
The compound which shows metamerism is :
The value of coefficient of volume expansion of glycerin is $5 \times 10^{-4}\text{ K}^{-1}$. The fractional change in the density of glycerin for a rise of $40^{\circ}\text{C}$ in its temperature is -
The enzyme enterokinase helps in conversion of