71. Woollen clothes keep the body warm because

1. 1. Wool increases the temperature of the body

   
   
   

   2. Wool is the bad conductor of the heat so it does not allow heat to flow out of the body

   
   
   

   3. Wool absorbs radiant heat from outer objects

   
   
   

   4. Wool rejects heat from outer objects

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: B

   N/A

---

72. In the winter season if we touch two blocks one of iron and another of wood in the early morning then the block of iron appears to be more cold because

1. 1. The temperature of the iron block is less than that of the wooden block

   
   
   

   2. Iron is a good conductor of heat in comparison of the wood

   
   
   

   3. Iron is a bad conductor of heat in comparison of the wood

   
   
   

   4. The block of iron is heavier than the wooden block

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: B

   N/A

---

---

73. A hollow sphere of radius R, a hollow cube of side R and thin circular plate of radius R made up of the same material, are all heated to 20°C above room temperature. When left to cool in the room, which of them will reach the room temperature first?

1. 1. Circular plate

   
   
   

   2. Cube

   
   
   

   3. Sphere

   
   
   

   4. All of them will reach the room temperature at the same time

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: C

   N/A

---

74. The pressure exerted on the walls of the container by a gas is due to the fact that the gas molecules

1. 1. Lose their kinetic energy

   
   
   

   2. Stick to the walls

   
   
   

   3. Are accelerated towards the walls

   
   
   

   4. Change their momenta due to collision with the walls

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: D

   N/A

---

---

75. Two blocks of ice when pressed together join to form one block because

1. 1. Of heat produced during pressing

   
   
   

   2. Of cold produced during pressing

   
   
   

   3. Melting point of ice increases with increase of pressure

   
   
   

   4. Melting point of ice decrease with increase of pressure

   
   
   

---

1. View Hint View Answer Discuss in Forum

   N/A

   Correct Option: D

   N/A

---