Q. No.Consider the equations
\(P=\operatorname{Lim}_{\Delta s \rightarrow 0} \frac{F}{\Delta S} \text { and } P_{1}-P_{2}=\rho g z .\)
In an elevator accelerating upward
1. both the equations are valid
2. the first is valid but not the second
3. the second is valid but not the first
4. both are invalid
\(P=\operatorname{Lim}_{\Delta s \rightarrow 0} \frac{F}{\Delta S} \text { and } P_{1}-P_{2}=\rho g z .\)
In an elevator accelerating upward
The three vessels shown in the figure have the same base area. Equal volumes of a liquid are poured in the three vessels. The force on the base will be:
 |
 |
 |
| A | B | C |
| 1. | maximum in vessel A |
| 2. | maximum in vessel B |
| 3. | maximum in vessel C |
| 4. | equal in all the vessels |
Equal mass of three liquids are kept in three identical cylindrical vessels \(A\), \(B\) and \(C\). The densities are \(\rho_A,~\rho_B,~\rho_C\) with \(\rho_A<\rho_B<\rho_C\) . The force on the base will be:
| 1. | maximum in vessel \(A\) |
| 2. | maximum in vessel \(B\) |
| 3. | maximum in vessel \(C\) |
| 4. | equal in all the vessels |
The figure shows a siphon. The liquid shown is water. The pressure difference PB – PA between the points A and B is
1. 400 N m–2
2. 3000 N m–2
3. 1000 N m–2
4. zero
A beaker containing a liquid is kept inside a big closed jar. If the air inside the jar is continuously pumped out, the pressure in the liquid near the bottom of the liquid will:
| 1. | increase |
| 2. | decrease |
| 3. | remain constant |
| 4. | first decrease and then increase |
The pressure in a liquid at two points in the same horizontal plane are equal. Consider an elevator accelerating upward and a car accelerating on a horizontal road. The above statement is correct in
1. the car only
2. the elevator only
3. both of them
4. neither of them
Suppose the pressure at the surface of mercury in a barometer tube is P1 and the pressure at the surface of mercury in the cup is P2.
1. P1 = 0, P2 = atmospheric pressure
2. P1 = atmospheric pressure, P2 = 0
3. P1 = P2 = atmospheric pressure
4. P1 = P2 = 0
A barometer kept in an elevator reads 76 cm when it is at rest. If the elevator goes up with increasing speed, the reading will be
1. zero
2. 76 cm
3. < 76 cm
4. > 76 cm
A barometer kept in an elevator accelerating upward reads 76 cm. The air pressure in the elevator is
1. zero
2. 76 cm
3. < 76 cm
4. > 76 cm
To construct a barometer, a tube of length 1 m is filled completely with mercury and is inverted in a mercury cup. The barometer reading on a particular day is 76 cm. Suppose a 1 m tube is filled with mercury up to 76 cm and then closed by a cork. It is inverted in a mercury cup and the cork is removed. The height of mercury column in the tube over the surface in the cup will be
1. zero
2. 76 cm
3. > 76 cm
4. < 76 cm
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