1.a barometer kept in an elevator accelerating upwardreads 76 cm. Air pressure in elevator isa)76cm b)<76cm c)>76cm d)0 . pls explain

2.)a solid is immersed in liquid ,The force exerted by the liquid on solid will

a)increase if it is pushed deeper inside the liquid

b)change if its orientation is changed

c)decrease if it is taken partially out of liquid

d)be in vertically upward direction

3) A closed vessel is half filled with water . There is a hole near the top of the vessel and air is pumped out from this hole.

a)The water level will rise up in the vessel.

b)the pressure at surface of water will decrease

explain why b)is correct but option a) is incorrect.

4)Water flows through 2 identical tubes A and B. A volume "V"of water passes through the tube A and 2V through B in a given time, which of the following may be correct?

a)flow in tubes are steady.

b)flow in both tubes are turbulent

c)flow is steady in A but turbulent in B

d)flow is steady in B but turbulent is A

Let's break down each of your questions step by step, providing clear explanations and reasoning for each scenario.

1. Barometer in an Accelerating Elevator

When a barometer is kept in an elevator that is accelerating upward and reads 76 cm, we need to consider the effects of acceleration on air pressure. The correct answer is c) >76 cm.

Here's why: A barometer measures atmospheric pressure, which is influenced by the weight of the air above it. When the elevator accelerates upward, it creates an additional force acting on the barometer. This force effectively increases the pressure exerted on the barometer, causing it to read a value greater than the actual atmospheric pressure outside the elevator. Therefore, the air pressure inside the elevator must be greater than 76 cm.

2. Force Exerted by Liquid on a Solid

When a solid is immersed in a liquid, the force exerted by the liquid on the solid is influenced by several factors. The correct answer here is d) be in vertically upward direction.

This upward force is known as buoyancy, which acts against the weight of the solid. According to Archimedes' principle, the buoyant force is equal to the weight of the liquid displaced by the solid. While the force may change if the solid is pushed deeper (option a) or partially taken out (option c), the direction of the buoyant force remains vertically upward regardless of the solid's orientation (option b). Thus, the force is always directed upwards.

3. Water Level in a Closed Vessel with Air Pumped Out

In a closed vessel that is half-filled with water, if air is pumped out from a hole near the top, the correct statement is b) the pressure at the surface of the water will decrease.

As air is removed from the vessel, the pressure above the water decreases. This reduction in pressure allows the water to exert less force against the air pressure, which can lead to a rise in the water level due to the external atmospheric pressure acting on the water's surface. However, option a) is incorrect because the water level does not necessarily rise; it may remain the same or even lower depending on the pressure dynamics. The key point is that the water level is influenced by the pressure difference created by the removal of air.

4. Water Flow in Identical Tubes

When considering the flow of water through two identical tubes A and B, where a volume "V" passes through tube A and 2V through tube B in a given time, the most appropriate answer is a) flow in tubes are steady.

Steady flow means that the velocity of the fluid at any given point does not change over time. Since both tubes are identical and the flow rates are consistent (V in A and 2V in B), it indicates that the flow can be steady in both tubes. However, if the flow rate in tube B is significantly higher, it could potentially lead to turbulence, but without additional information about the flow characteristics, we cannot definitively conclude that the flow in tube B is turbulent. Thus, option a is the safest choice based on the information provided.

Each of these scenarios illustrates fundamental principles of physics, such as pressure dynamics, buoyancy, and fluid flow. Understanding these concepts helps us grasp how forces and pressures interact in different environments.