TN State Board 10th Science Question Paper 2021

A rocket works on the principles of Newton’s third law of motion and the law of conservation of linear momentum. When hot gases are expelled backward from the rocket, an equal and opposite reaction pushes the rocket forward. Hence, both (a) and (c) are correct. Newton’s law of gravitation is not the principle used for propulsion.

The SI unit of resistance is ohm ($\Omega$). Mho is the unit of conductance, joule is the unit of energy, and watt is the unit of power.

The speed of sound in air at NTP is about 340 m/s. The other values are not correct because they are either far too large or far too small compared to the actual speed of sound.

Radioactivity is measured in different units depending on the context. Roentgen is used for exposure, Curie and Becquerel are units of radioactivity, so the correct option is all of the above.

Duralumin is the alloy commonly used in the manufacturing of pressure cookers because it is light, strong, and corrosion resistant. Brass and bronze are not commonly used for this purpose, and magnalium is used in specific applications but not typically for pressure cookers.