Define heat capacity and state its SI unit.
Heat capacity is defined as the total amount of heat required to raise the temperature of a body by 10 C. It is represented by S.
Its SI unit is JK-1.
The distance between two bodies is doubled. How is the magnitude of the gravitational force between them affected?
Force of gravity given by
Therefore, the force of gravity is reduced four times.
A solid of mass 50 g at 150°C is placed in 100 g of water at 11°C, when the final temperature recorded is 20°C. Find the specific heat capacity of the solid. (specific heat capacity of water = 4.2 J/g°C)
Mass of the solid, ms = 50 g
Initial temperature of the solid, ts = 150°C
Mass of water, mw = 100 g
Temperature of water, tw = 11°C
Final temperature of the mixture, t = 20°C
According to the principle of calorimetry,
Heat gained by water = Heat lost by the solid
∴100x 4.2 x(20 -11) = 50 xcs x (150-20)
3780 = 6500cs
3780/6500 = 0.581 J/g°C
If the power of a motor is 100 kW, at what speed can it raise a load of 50,000 N?
Given, power of the motor, P = 100 kW =100 × 1000 W = 105 Watt
and force, F = 50000 N.
Now, from the definition of power,
Hence, the motor can lift the load with a speed of 2 ms-1.
Which class of lever will always have MA > 1 and why?
A second Class lever (class II) will always have MA > 1. This is because the load is between the fulcrum and the effort. So, the effort arm is always greater than the load arm. Hence, MA = E/L > 1.
Why is the base of a cooking pan generally made thick?
The base is made up of metal, which is a good conductor of heat. By making the base of a cooking pan thick, its thermal capacity becomes large and it imparts sufficient heat energy at a low temperature to the food for proper cooking.
A brass ball is hanging from a stiff cotton thread. Draw a neat labelled diagram showing the forces acting on the brass ball and cotton thread.
A brass ball is hanging thus, weight mg of ball acts downwards and tension acts on the thread in the upward direction.
How is the refractive index of a material related to:
(i) real and apparent depth?
(ii) velocity of light in vacuum or air and the velocity of light in a given medium?
(i) When an object is placed under water (any other medium) than observing it from
outside the water (or medium) it appears to be raised above.
The ratio of real depth and apparent depth is equal to the refractive index of the
Refractive index, µ =
(ii) The relation between Refractive Index and Velocity of Light.
The refractive index of the medium is the ratio of the velocity of light in vacuum (or air) to the velocity of light in that medium.
Why is a jack screw provided with a long arm?
A jack, screw jack or jackscrew is a mechanical device used as a lifting device to lift heavy loads or to apply great force. A jack screw is provided with a long arm in order to have the effort less than the load.
Moment of force (torque, which is responsible for turning effect of the body)
Rotation is given by the moment
Torque = Force x perpendicular length
Therefore, the long arm of the jack screw, the more force it can apply.
State the conditions required for total internal reflection of light to take place.
The necessary Conditions for total internal reflection to take place are
(i) The light must travel from a denser medium to a rarer medium.
(ii) The angle of incidence must be greater than the critical angle (ic) for the pair of media.