Normal Force

Q. The number of points where normal forces are acting on the boy are__________.

1. three
2. two
3. five
4. four

Q. An automobile tire is filled completely with water. The tire is mounted on an axle so that the tire is in a vertical plane. How does the pressure vary inside the tire with (a) no additional force applied; (b) a strong pushing up on the bottom of the tire: (c) a strong force pushing down on the top the tire

1. The pressure is significantly greater at the top.
2. The pressure is approximately the same everywhere.
3. The pressure is significantly greater at bottom.
4. The pressure variation cannot be determined without more information

Q. If $\theta$ is instantaneous angle which the line joining the particle and the centre of the loop makes with the vertical, then identify the correct statement(s) related to the normal reaction $N$ between the block and the surface

1. The maximum value $N$ occurs at $\theta =0$
2. The minimum $N$ occurs at $N=\pi$ for $H>5R/2$
3. The value of $N$ becomes negative for $\pi /2<\theta <3\pi /2$
4. The value of $N$ becomes zero only when $\theta \ge \pi /2$

Q. Two metal spheres are falling through a liquid of density $2\times {10}^{3}kg/m^3$ with the same uniform speed. The density of the materials of the spheres are $8\times {10}^{3}kg/m^3$ and $11\times {10}^{3}kg/m^3$ respectively. The ratio of their speeds are:

1. $\sqrt{\frac{11}{8}}$
2. $\sqrt{\frac{3}{2}}$
3. $\frac{3}{2}$
4. $\frac{11}{8}$

Q. A man is standing on incline which makes angle $\theta$ with horizontal and rain is falling vertically with respect to man. Now man starts walking along the incline

1. If man walks up the incline, rain may appear to come horizontal
2. If man walks down the incline, rain may appear to come horizontally
3. No matter whether man walks up or down, rain can never appear to come horizontal
4. If man walks (up or down) along incline rain may appear to come along the inclined

Q. A wooden sphere rolls down to two different inclined planes of the same height but different inclines. Will it reach the bottom with the same speed in each case?

Q. If a pushing force an angle $\alpha$ with horizontal is applied on a block of mass $m$ placed on horizontal table and angle of function is $\beta$, then minimum magnitude of force required to move the block is

1. $\frac{mg\sin \beta }{\cos \left[\alpha -\beta \right]}$
2. $\frac{mg\sin \beta }{\cos \left[\alpha +\beta \right]}$
3. $\frac{mg\sin \beta }{\sin \left[\alpha +\beta \right]}$
4. $\frac{mg\cos \beta }{\cos \left[\alpha -\beta \right]}$

Q. A wooden piece is balanced by a brass weight in a sensitive balance. Now the pan contained by wooden piece is covered by a bell jar and then evacuated;

1. the pan containing the wooden piece will go up
2. the pan containing the wooden piece will go down
3. the beam will remain horizontal
4. nothing can be said definitely

Q. A block of mass $m$ is pulled along a horizontal surface by a horizontal rope of mass $1kg$. A force of $15N$ is applied at the free end of the rope. The force exerted by the block on the rope is $13.5N$. the mass $m$ of the block is:

Q. L shaped rod is hinged from O in vertical plane at its end as shown in figure. Rod is in equilibrium position then, Determine $\varphi$.

1. ${tan}^{-1}\left(\frac{1}{3}\right)$
2. ${tan}^{-1}\left(\frac{1}{2}\right)$
3. $\frac{\pi }{4}$
4. None