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A U tube with both ends open to the atmosphere, is partially filled with water. Oil, which is immiscible with water, is poured into one side until it stands at a distance of 10 mm above the water level on the other side. Meanwhile the water rises by 65 mm from its original level (see diagram). The density of the oil is
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A rectangular film of liquid is extended from (4cm × 2cm) to (5cm × 4cm). If the work done is 3 × 10−4J, the value of the surface tension of the liquid is
Work done = Surface tension of film x Change in area of the film
Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at 100°C, while the other one is at 0°C. If the two bodies are brought into contact, then, assuming no heat loss, the final common temperature is
Since, heat capacity of material increases with increase in temperature so, body at 100 °C has more heat capacity than body at 0°C. Hence, final common temperature of the system will be closer to 100\°C
∴ Tc > 50°C
Coefficient of linear expansion of brass and steel rods are α1 and α2. Length of brass and steel rods are l1 and l2 respectively. If (l2 − l1) is maintained same at all temperatures, which one of the following relations holds good?
Linear expansion of brass = α1
Linear expansion of steel = α2
Length of brass rod = l1
Length of steel rod = l2
On increasing the temperature of the rods by ΔT, new lengths would be
l1′ = l1(1 + α1ΔT) ........(i)
l2′ = l2(1 + α2ΔT) .........(ii)
Subtracting eqn. (i) from eqn. (ii), we get
l2′ − l1′ = (l2 − l1) + (l2α2 − l1α1)ΔT
According to question,
l2′ − l1′ = l2 − l1 (for all temperatures)
∴ l2α2 − l1α1 or l1α1 = l1α2
A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250nm is U1, at wavelength 500 nm is U2 and that at 1000 nm is U3 Wien's constant, b = 2.88 × 106nmK. Which of the following is correct?
An airplane of a total wing area of 120 m2 is in a level flight at some height. If the pressure difference between the upper and lower surface is 2.5 kPa, then the mass of the airplane is: [Take g = 10 ms-2]
A liquid is poured into three vessels of the same base area and equal heights as shown in the figure, then:
Step 1: Find the pressure at the bottom in all cases
Pb = P0 + ρgh
Step 2: Find thrust at the base of each vessel
F = PbA
= PbA
As the pressure and the area is the same for all the cases. So, the force on the base will be equal for all the vessels.
If pressure at half the depth of a lake is equal to 2/3rd the pressure at the bottom of the lake, then the depth of the lake is:
The value of g at a place decreases by 2%. Then, the barometric height of mercury:
If the value of g is decreased by 2% then h will increase by 2%.
A siphon in use is demonstrated in the following figure. The density of the liquid flowing in the siphon is 1.5 gm/cc. The pressure difference between the point P and S will be:
As both the points are at the surface of the liquid and in the open atmosphere. So, both the points possess similar pressure equal to 1 atm. Hence the pressure difference will be zero.
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