Normal Force

Q. What force is the Normal Force a reaction for?

1. Gravitational Force
2. Abnormal Force
3. Electromagnetic Force from the Block
4. None of these

Q.

Write down the units and dimensional formulae of following physical quantities:
$Strain=\frac{elongation}{actuallength}$

Q. What should be the acceleration ${}^{\prime }{a}^{\prime }$ of the box shown in figure so that the block of mass $m$ exerts a force $\frac{mg}{4}$ on the floor of the box ? (where $g$ is acceleration due to gravity)

1. $\frac{3g}{4}$
2. $\frac{g}{4}$
3. $\frac{2g}{4}$
4. $\frac{4g}{4}$

Q. Statement – 1: Normal reaction acting on a body is always perpendicular to the surface. Statement – 2: Normal reaction is a component of contact force.

1. STATEMENT – 1 is True, STATEMENT – 2 is True; STATEMENT – 2 is a correct explanation for STATEMENT – 1
2. STATEMENT – 1 is True, STATEMENT – 2 is True; STATEMENT – 2 is NOT a correct explanation for STATEMENT – 1
3. STATEMENT – 1 is True, STATEMENT – 2 is False
4. STATEMENT – 1 is False, STATEMENT-2 is True

Q. The mass of a body indicated by a weighing machine in a lift at rest is found to be $m$. If the lift is going up with an acceleration $a$, then the new reading shown by the scale will be

1. $m(1-\frac{a}{g})$
2. $m(1+\frac{a}{g})$
3. $m$
4. Zero

Q. A block of mass $m$ is placed on the floor of lift which is moving with velocity $v=4t^2$, where $t$ is time in second and velocity in $\text{m/s}$. Find the time at which normal force on the block is three times of its weight.

1. $\left(\frac{3g}{8}\right)s$
2. $gs$
3. $\frac{g}{4}s$
4. $3gs$

Q. The elevator shown in figure is descending with an acceleration of $2{\text{ms}}^{-2}$. The mass of the block $A=0.5\text{kg}$. The force exerted by the block $A$ on the block $B$ is $(g=10{\text{ms}}^{-2})$

1. $2N$
2. $4N$
3. $6N$
4. $8N$

Q. What should be the acceleration ${}^{\prime }{a}^{\prime }$ of the box shown in figure so that the block of mass $m$ exerts a force $\frac{mg}{4}$ on the floor of the box ? (where $g$ is acceleration due to gravity)

1. $\frac{3g}{4}$
2. $\frac{g}{4}$
3. $\frac{2g}{4}$
4. $\frac{4g}{4}$