Gravitational Force

Q. The radius of Earth is about $6400\text{km}$ and that of Mars is $3200\text{km}$. The mass of the Earth is about $10$ times the mass of Mars. If an object weighs $200\text{N}$ on the surface of Earth, its weight on the surface of Mars will be

1. $20\text{N}$
2. $8\text{N}$
3. $80\text{N}$
4. $40\text{N}$

Q.

The centre of mass of a body

1. always lies inside the body

2. always lie outside the body

3. may lie inside or outside the body

4. lies at the geometrical center

Q. The change in the value of $g$ at a height $h$ above the surface of the earth is the same as at a depth $d$ below the surface of the earth. When both $d$ and $h$ are much smaller than the radius of earth, then which one of the following is correct?

1. $d=\frac{3h}{2}$
2. $d=\frac{h}{2}$
3. $d=h$
4. $d=2h$

Q.

What is a meta centre ?

Q.

If the distance between two masses is doubled, the gravitational attraction between them

1. Is reduced to a quarter

2. Is reduced to half

3. Is doubled

4. Becomes four times

Q. Riya buys a bag of sugar of weight $W$ at a place on the equator. She takes it to Antarctica, the weight of the sugar bag will

1. increase
2. decrease
3. remain the same
4. can't predict

Q. A body of mass $m$ is tied to one end of spring and whirled round in a horizontal plane with a constant angular velocity. The elongation in the spring is one centimeter. If the angular velocity is doubled, the elongation in spring is 5 $cm$. The original length $L$ of spring (in $cm$ ) is

Q. A square shaped hole of side $l=\frac{a}{2}$ is carved out at a distance $d=\frac{a}{2}$ from the centre ‘O’ of a uniform circular disk of radius $a$. If the distance of the centre of mass of the remaining portion from O is$-\frac{a}{X}$, value of $X$ (to the nearest integer) is

Q. Gravitation is the phenomenon of interaction between:

1. point masses only
2. any arbitrary shaped
3. planets only
4. None of these

Q. The position vector of the centre of mass $r_{\text{cm}}$ of an asymmetric uniform bar of negligible area of cross - section as shown in figure is:

1. ${\overrightarrow{r}}_{\text{cm}}=\frac{11}{8}L\hat{x}+\frac{3}{8}L\hat{y}$
2. ${\overrightarrow{r}}_{\text{cm}}=\frac{13}{8}L\hat{x}+\frac{5}{8}L\hat{y}$
3. ${\overrightarrow{r}}_{\text{cm}}=\frac{5}{8}L\hat{x}+\frac{13}{8}L\hat{y}$
4. ${\overrightarrow{r}}_{\text{cm}}=\frac{3}{8}L\hat{x}+\frac{11}{8}L\hat{y}$

Q. According to Newton's law of gravitation, every object in the universe attracts every another object, then why dont objects move under the influence of this force of gravitation?

Q. How to prove that the value of g is 9.8m/s²

Q.

When we use 'g' as positive and negative in motion under gravity.?

Please explain I'm always confused in this.

Q. A block of mass m is placed on a smooth horizontal surface as shown. The weight (mg) of the block and normal reaction (N) exerted by the surface on the block

1. Form action - reaction pair
2. Act in same direction
3. Both (a) and (b)
4. Balance each other

Q. What is the difference between the centre of gravity and the centre of mass?

Q.

Differentiate between the following.

Wedge and inclined plane

Q. List 2-3 differences between centre of mass and centre of gravity.

Q.

Newton Is The Unit Of Which Quantity.

1. Mass.

2. Force.

3. Gravity.

4. Acceleration.

Q. If the action force acting on a body is gravitational in nature, the reaction force -

1. may be a force of any origin.
2. may be a gravitational or contact force.
3. may be a contact force.
4. must be gravitational too.

Q.

A steel column pinned at both ends has a bucking load of 160 kN. If the column is effectively held in position and restrained against rotation at one end but neither held in position nor restrained against rotation at the other end, then its bucking load will be kN.

1. 40

Q. A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is $\overrightarrow{F}$, the net force on the remaining three arms of the loop is

1. $\overrightarrow{F}$
2. $-3\overrightarrow{F}$
3. $-\overrightarrow{F}$
4. $3\overrightarrow{F}$

Q.

The gravitational force cause?

1. Tides

2. None of them

3. Motion of moon

4. Both A and C

Q.

Define the following
(a) Newton

(b) Kilogram Force

(c) Pascal

(d) Gram Force

Q. A uniform metre stick of 200 g is suspended from the ceiling through two vertical strings of equal lengths fixed at the ends. A small object of mass 20 g is placed on the stick at a distance of 70 cm from the left end. Find the tensions in the two strings.

Q.

If two masses are equal and made of the same material, how will the force of attraction vary with separation?

Q.

Any plane surface that is tilted or inclined to the horizontal ________ .

Q. The mass density of a planet of radius $R$ varies with the distance $r$ from its centre as $\rho \left(r\right)={\rho }_0(1-\frac{r^2}{R^2}).$ Then the gravitational field is maximum at:

1. $r=\sqrt{\frac{3}{4}}R$
2. $r=R$
3. $r=\frac{1}{\sqrt{3}}R$
4. $r=\sqrt{\frac{5}{9}}R$

Q. A body weighs $250N$ on the surface of the earth. How much will it weigh half way down to the centre of the earth.?

1. $125N$
2. $150N$
3. $175N$
4. $250N$.

Q. If Z = A /A-B and A and B are measured with error *A and *B respectively then relative error in Z that is *Z /Z is equal to

Q. Select the correct choice(s)

1. The gravitational field inside a spherical cavity within a spherical planet must be non zero and uniform.
2. When a body is projected horizontally at an appreciable large height above the earth, with a velocity less than orbital velocity, it will fall to the earth along a parabolic path
3. A body of zero total mechanical energy placed in a gravitational field will escape the field
4. Earth's satellite must be in the equatorial plane.