Question 2 :
Which of the following methods of measurement of time is suitable for a race?

Question 4 :
A boy on a cycle pedals a circle of 20 metres radius at a speed of 20 metre/sec. The combined mass of the boy and the cycle is 90 kg. The angle that the cycle makes with the vertical so that it may not fall is $\left( {g = 9.8m/\sec ^2 } \right)$<br>

Question 7 :
A person travelled a distance of $100 m $ in $10$ seconds. What is the speed of the person?

Question 8 :
Arunoday started walking towards his office at $9 AM$ in the morning. He reached his office at $9:30AM$. He started walking again to reach home in same time. What is the total distance covered by Arunoday if the average speed of Arunoday is $4 km/hr$?

Question 9 :
A $120 m$ long train is moving towards west at a speed of $5 {m}/{sec}$ crosses the train. The time taken by the bird to cross the train would be

Question 10 :
When a simple pendulum is taken from the Equator to the Pole, its period of oscillation will :

Question 11 :
A constant force acts on a mass m at rest. Velocity acquired in travelling a fixed distance is directly proportional to:

Question 12 :
A 2 kg object moving with the speed of 2 m/s collides with 4 kg objects, which is at rest. if the final velcocities of the odjects are same, then what would be the final velocity?

Question 14 :
Assertion: Air is a good conductor of heat Reason: It's molecules are in close contact with each other

Question 15 :
If object A and object B has no transfer of heat, then they both are in

Question 16 :
One litre of water at $30^{o}C$ is mixed with one litre of water at $50^{o}C$. The temperature of the mixture will be

Question 18 :
.................. surface absorbs more heat than any other surface under identical conditions.

Question 19 :
Assertion: Snow is better insulator than ice. Reason: Snow contain air packet and air is good insulator of heat.

Question 22 :
Assertion: The range of clinical thermometer is between $35 ^\circ C$ and $42 ^\circ C$ Reason: The normal temperature of the human body is about $37 ^\circ C$ .Our body temperature cannot fall below $35 ^\circ C$ or rise above $42 ^\circ C$.

Question 23 :
Assertion: We feel cold on touching the ice. Reason: Ice is a solid form of water.

Question 25 :
Assertion: In natural convection, the fluid motion is caused due to density difference produced by temperature gradient. Reason: In forced convection, the fluid is forced to flow along the solid surface by means of fans or pumps.

Question 26 :
The amount of heat required to raise the temperature of 1 kilogram of water by $1\:^oC$ is called :<br/>

Question 28 :
Assertion: Though air is a bad conductor yet a body kept in air loses heat quickly.<br/> Reason: The heat loss is mainly due to radiation.

Question 29 :
There are two hollow spheres made of different materials, one with double the radius and one fourth wall thickness of the other are filled with ice. If the time taken for melting the ice completely in larger sphere is $25$ minutes and that for smaller sphere is $16$ minutes, the ratio of the thermal conductivity of the larger sphere to the smaller sphere is :

Question 30 :
Assertion: The equivalent thermal conductivity of two plates of same thickness in contact is less than the smaller value of thermal conductivity Reason: For two plates of equal thickness in contact the equivalent thermal conductivity is given by:<br><br>$\cfrac{1}{K}=\cfrac{1}{K}_{1}+\cfrac{1}{K}_{2}$

Question 31 :
The steam point and the ice point of a mercury thermometer are marked $80^0$ and $20^0.$&#160; what will be the temperature in centigrade mercury scale when this thermometer reads $32^0$

Question 32 :
Mercury is often used in clinical thermometers. Which one of the following properties of mercury is not a reason for this ?