Q. A boy uses a single fixed pulley to lift a load of $50$ Kgf to some height. another boy uses a single movable pulley to lift the same load to the same height. Compare the effort applied by them. Give a reason to support your answer.

Q. State two characteristics of a good thermion emitter.

Q. How is the frequency of a stretched string related to its tension?

Q. Distance moved by the effort.

Q. Which class of lever will always have MA$>1$ and why?

Q. Why is the base of a cooking pan generally made thick?

Q. State two factors upon which the rate of emission of thermions depends.

Q. Work done by the effort.

Q. Name the process used for producing electricity using nuclear energy.

Q. State the conditions required for total internal reflection of light to take place.

Q. Why is a jack screw provided with a long arm?

Q. M.A. of the pulley system.

Q. An electric bulb of resistance $500\Omega$, draws a current of $0.4$A. Calculate the power of the bulb and the potential difference at its end.

Q. How is the refractive index of a material related to real and apparent depth?

Q. State two causes of energy loss in a transformer.

Q. How is the refractive index of a material related to velocity of light in vacuum or air and the velocity of light in a given medium?

Q. An enemy plane is at a distance of $300$km from a radar. In how much time the radar will be able to detect the plane? Take velocity of radio-waves as $3\times {10}^{8}m{s}^{-1}$.

Q. If the power of a motor be $100$kW, at what speed can it raise a load of $50,000$N?

Q. A brass ball is hanging from a stiff cotton thread. Draw a neat labelled diagram showing the forces acting on the brass ball and the cotton thread.

Q. A solid of mass $50$g at ${150}^o$C is placed in $100$g of water at ${11}^o$C, when the final temperature recorded is ${20}^o$C. Find the specific heat capacity of the solid. (Specific heat capacity of water $4.2$J$/g^o$C

Q. How does uniform circular motion differ from uniform linear motion?

Q. How is the frequency of a stretched string related to its length?

Q. The human ear can detect continuous sounds in the frequency range from $20$Hz to $20,000$Hz. Assuming that the speed of sound in air is $330m{s}^{-1}$ for all frequencies, calculate the wavelengths corresponding to the given extreme frequencies of the audible range.

Q. Define specific resistance and state its SI unit.

Q. The distance between two bodies is doubled. How is the magnitude of gravitational force between them affected?

Q. Draw a ray diagram to show the refraction of a monochromatic ray through a prism when it suffers minimum deviation.

Q. Draw a diagram of the arrangement.

Q. Define heat capacity and state its SI unit.

Q. What is the weight of the half metre rule?

Q. When does the nucleus of an atom tend to be radioactive?