11
Why is water not a suitable barometric liquid? ANSWER Water is not a suitable barometric fluid as it has low density (~1000kg/m3) which would require a barometer around 11 meters in length, which is quite impractical. Also, it is transparent and quite dull in appearance which would make observing reading quite difficult coupled with the fact that is it has quite high specific heat which would also make it less responsive to temperature changes. So, we normally use mercury as a barometric fluid. why is it difficult to stop bleeding from cut in human body at high altitudes? ANS: Due to Bernoulis Theorem we can answer this question, as; at high altitudes the pressure outside is less(means less than 1atm) and pressure inside our body is more...therefore this leads to rupturing of blood vessels and causes bleeding(mainly nose bleeding). difference between centre of gravity and centre of mass ANSWER The center of mass is a geometrical measurement considering only mass distribution and not weight distribution. Centre of mass is a mathematically defined point for an object, which is unaffected by external field/force unless it is deformed by the external field/ force. However, centre of gravity is a point from where net weight is assumed to act. Clearly it depends on gravity which is an external force. Normally, centre of mass and gravity are same, this is because Earth’s gravitational field is uniform. Now, consider a situation in which gravitational field is non-uniform. Also, imagine a very long uniform rod. If you consider two parts of rod with same mass, the force of gravitation (weight) will be different on both instead of same mass. Due to which, its centre of gravity and center of mass will be different. Because of this, the position of centre of mass of this rod will be different from that of centre of weight. Normally, on Earth gravity is uniform so center of mass and gravity are same for most of the objects. But again be cautious!

Why is water not a suitable barometric liquid.docx

Embed Size (px)

Citation preview

Why is water not a suitable barometric liquid?ANSWER

Water is not a suitable barometric fluid as it has low density (~1000kg/m3) which would require a barometer around 11 meters in length, which is quite impractical. Also, it is transparent and quite dull in appearance which would make observing reading quite difficult coupled with the fact that is it has quite high specific heat which would also make it less responsive to temperature changes.So, we normally use mercury as a barometric fluid.why is it difficult to stop bleeding from cut in human body at high altitudes? ANS:Due to Bernoulis Theorem we can answer this question,as;at high altitudes the pressure outside is less(means less than 1atm) and pressure inside our body is more...therefore this leads to rupturing of blood vessels and causes bleeding(mainly nose bleeding).

difference between centre of gravity and centre of massANSWER

The center of mass is a geometrical measurement considering only mass distribution and not weight distribution. Centre of mass is a mathematically defined point for an object, which is unaffected by external field/force unless it is deformed by the external field/ force.However, centre of gravity is a point from where net weight is assumed to act. Clearly it depends on gravity which is an external force.Normally, centre of mass and gravity are same, this is because Earths gravitational field is uniform.Now, consider a situation in which gravitational field is non-uniform. Also, imagine a very long uniform rod.If you consider two parts of rod with same mass, the force of gravitation (weight) will be different on both instead of same mass. Due to which, its centre of gravity and center of mass will be different.Because of this, the position of centre of mass of this rod will be different from that of centre of weight.Normally, on Earth gravity is uniform so center of mass and gravity are same for most of the objects. But again be cautious!

what is the derivation of moment of inertia of solid cone? ANSWER

A cone can be through as a placement of thin disk one by one with constantly decreasing radius. Let mass of the cone be M, base radius R and height H. be the density of the cone.Let us consider a thin disk at a distance y from the base of thickness dyWe have

derive the centre of mass of a solid cone and a hollow cone.For a solid cone,Let (Xc,Yc) are the coordinates of center of mass. Then,

For symmetry consider the center of mass at Xc=0.Divide the cone in horizontal disks of mass then,dm=dV where, is the density of material. (constant)In this case,where r is the radius of the cone at an arbitrary heightdy.radius of cone depends upon the height of the cone. So,y=0 ; r=R (R is the base radius of the cone)y=h ; r=0.Using point-slope form:

Now, the volume

So,

So, the center of mass of solid cone is at the quarter height on the line joining from center of the base to the vertex.For hollow cone,Let (Xc,Yc) are the coordinates of center of mass. Then,

For symmetry consider the center of mass at Xc=0.For hollow cone,dm= dA

So, the center of mass of a hollow cone is at one-third of the height on the line joining from center of the base to the vertex.derive the moment of inertia of rod, ring, disc, cylinder, sphere and cone?Here are the derivations of MI of rod, ring, cylinder and sphere.

Moment of inertia of a cylinder (hollow) of radius r about its central axis (shown in red line)

Moment of inertia of a cylinder (solid) of radius r about its central axis (shown in red line)Before we derive the MI of solid cylinder let us derive the MI of a circular disk.

Consider a small area strip element at a distance x from the centre of the disk of radiusR.Let mass of the disk = m

a train has started from rest and had attained a ceratin speed. there is a pendulum inside the train which makes angle X as angular displacement, then what is the speed of the train? ANSWER

Look at the figure below to understand the scenario:

When train starts from rest and acquires a velocity then that means that the train is accelerating in the direction of motion.Since it is accelerating in the direction of the motion then an net force will act on the bob of the pendulum and it will be in a direction opposite to the motion of the train as shown above:Now, if at any instant the bob is making an angle 'X' from the vertical then:

tanx=abgab=gtanXnow,fromfirstequationofmotion:v=u+atv=0+abtv=gtanXt

What is gravitational centreanswer

Centre of gravity is a point on in object from where net weight is assumed to act.There is no one formula for center of gravity of an object. The center of gravity of an object is found from its mass distribution and using geometry. Also the center of gravity depends on the gravitational field.