CBSE
Multiple Choice QuestionsA raft of wood of mass 120 kg floats in water. The weight that can be put on the raft to make it just sink should be (draft = 600 kg/m3) :
80 kg
50 kg
60 kg
30 kg
Eight small drops, each of equal charges and radii are coalesce to form a big drop. The capacity of bigger drop in comparison to each smaller drop will be :
4 times
2 times
32 times
8 times
Given that the surface tension of water is 75 dyne/cm, its density 1 g/cc and angle of contact zero, the height to which water rises in a capillary tube of 1 mm diameter is (Take g = 10 m/s2)
9.0 cm
7.5 cm
6.0 cm
3.0 cm
Mercury boils at 367°C. However, mercury thermometers are made such that they can measure temperature upto 500°C. This is done by:
maintaining vacuum above the mercury column in the stem of the thermometer
filling nitrogen gas at high pressure above the mercury column
filling oxygen gas at high pressure above the mercury column
filling nitrogen gas at low pressure above the mercury column
A wooden block is taken to the bottom of a deep, calm lake of water and then released. It rises up with a :
constant acceleration
decreasing aceleration
constant velocity
decreasing velocity
A hollow conducting sphere is placed in an electric field produced by a point charge placed at P as shown in the figure. Let VA, VB, VC be the potentials at points A, B and C respectively. Then :
VC > VB
VB > Vc
VA > VB
VA = VC
A tank is filled with water upto height H. When a hole is made at a distance h below the level of water, what will be the horizontal range of water jet?
2√h(H - h)
4√h(H + h)
4√h(H - h)
2√h(H + h)
An ice-cube of density 900 kg/m3 is floating in the water of density 1000 kg/m3 The percentage of volume of the ice-cube outside the water is:
20 %
35 %
10 %
25 %
The surface tension of the soap solution is T. The work done in forming a soap bubble of radius r, is :
The radius R of the soap bubble is doubled under isothermal condition. If T be the surface tension of soap bubble, the required surface energy in doing so is given by:
32πR2T
24πR2T
8πR2T
4πR2T
