MCQ 11 Mark
A metal in which even iron can float is:
AnswerThis is because the density of mercury is greater than the iron.
View full question & answer→MCQ 21 Mark
Two objects of different masses falling freely near the surface of moon would:
- ✓
Have same velocities at any instant.
- B
Have different accelerations.
- C
Experience forces of same magnitude.
- D
Undergo a change in their inertia.
AnswerCorrect option: A. Have same velocities at any instant.
We know,
$v = u + at$
$⇒ v = 0 + gt$
[Here, g is acc. Due to gravity on moon]
Thus, the equation of velocity for a freely falling body is independent of the mass of the body.
So, different masses that are dropped simultaneously with the same or zero initial velocity will have same velocity at any instant.
View full question & answer→MCQ 31 Mark
Consider the following information in respect of four objects $A, B, C$ and $D:$
| Object |
Density $(kg/m^3)$ |
Volume $(m^3)$ |
Mass $(kg)$ |
| $A$ |
$-$ |
$2$ |
$4000$ |
| $B$ |
$8000$ |
$4$ |
$-$ |
| $C$ |
$2000$ |
$-$ |
$1000$ |
| $D$ |
$-$ |
$4$ |
$2000$ |
Which object would float on water$?$ Answer This is because among these four objects, only the density of object $D$ is less than water.
View full question & answer→MCQ 41 Mark
A solid of density $900 \mathrm{~kg} / \mathrm{m}^3$ floats in oil as shown in the given diagram. The oil floats on water of density $1000 \mathrm{~kg} / \mathrm{m}^3$ as shown. The density of oil in $\mathrm{kg} / \mathrm{m}^3$ could be:
- A
$850$
- B
$900$
- ✓
$950$
- D
$1050$
AnswerThe solid object floats in oil because the density of the solid object is less than the oil. The oil floats in water because the density of oil is less than water.
Thus, the density of oil must be between density of solid and water.
View full question & answer→MCQ 51 Mark
An object is thrown vertically upwards with a velocity $u,$ the greatest height h to which it will rise before falling back is given by:
AnswerCorrect option: B. $\frac{\mu^2}{2\text{g}}$
At the maximum height $'h',$ the velocity becomes zero.
Using,
$\text{v}^2 = \mu^2 − 2\text{gh}$
$\Rightarrow 0 =\mu^2 − 2\text{gh}$
$\Rightarrow \text{h}=\frac{\mu^2}{2\text{g}}$
View full question & answer→MCQ 61 Mark
An object weighs $10N$ in air. When immersed fully in a liquid, it weighs only $8N.$ The weight of liquid displaced by the object will be:
AnswerWe know,
Buoyant force or weight of liquid displaced $=$ Actual weight $-$ Apparent weight
$⇒$ Weight of the liquid displaced $= 10 - 8 = 2 N.$
View full question & answer→MCQ 71 Mark
The relative densities of four liquids $P, Q, R$ and $S$ are $1.26, 1.0, 0.84$ and $13.6$ respectively. An object is floated in all these liquids, one by one. In which liquid the object will float with its maximum volume submerged under the liquid$?$
AnswerThis is because $R$ has the lowest density among the four.
View full question & answer→MCQ 81 Mark
The atmosphere consisting of a large number of gases is held to the earth by:
AnswerGravity of the earth holds the atmosphere consisting of a large number of gases.
View full question & answer→MCQ 91 Mark
In the relation $\text{F}=\text{G}\times\text{M}\times\frac{\text{m}}{\text{d}^2},$ the quantity $G:$
- A
Depends on the value of g at the place of observation.
- B
Is used only when the earth is one of the two masses.
- C
Is the greatest on the surface of the earth.
- ✓
Is of the same value irrespective of the place of observation.
AnswerCorrect option: D. Is of the same value irrespective of the place of observation.
This is because $G$ is constant in the given equation.
View full question & answer→MCQ 101 Mark
The force of attraction between two unit point masses separated by a unit distance is called:
- A
- B
Acceleration due to gravity.
- C
Gravitational field strength.
- ✓
Universal gravitational constant.
AnswerCorrect option: D. Universal gravitational constant.
View full question & answer→MCQ 111 Mark
he value of g on the surface of the moon:
- A
Is the same as on the earth.
- ✓
Is less than that on the earth.
- C
Is more than that on the earth.
- D
Keeps changing day by day.
AnswerCorrect option: B. Is less than that on the earth.
The value of g on moon is $\frac{1}{6}$ times its value on the earth.
View full question & answer→MCQ 121 Mark
An apple of mass $100\ g$ falls from a tree because of gravitational attraction between the earth and the apple. If the magnitude of force exerted by the earth on the apple be $F _1$, and the magnitude of force exerted by the apple on the earth be $F _2$, then:
- A
$F_1$ is very much greater than $F_2$
- B
$F_2$ is very much greater than $F_1$
- C
$F_1$ is only a little greater than $F_2$
- ✓
$F_1$ and $F_2$ are exactly equal.
AnswerCorrect option: D. $F_1$ and $F_2$ are exactly equal.
According to Newton's third law of motion, if an object exerts a force on another object, then the second object exerts an equal and opposite force on the first object.
View full question & answer→MCQ 131 Mark
The value of acceleration due to gravity of earth:
- A
Is the same on equator and poles.
- B
- ✓
- D
Increases from pole to equator.
Answerbecause its value decreases on moving near the equator.
View full question & answer→MCQ 141 Mark
The density of water is $1000\ kg/m^3$ and the density of copper is $8900\ kg/m^3.$ Which of the following statements is incorrect?
- A
$=\frac{\text{The density of a certain volume of copper}}{\text{The density of the same volume of water}}=8.9$
- ✓
$=\frac{\text{The volume of a certain mass of copper}}{\text{The volume of the same mass of water}}=8.9$
- C
$=\frac{\text{The weight of a certain volume of copper}}{\text{The weight of the same volume of water}}=8.9$
- D
$=\frac{\text{The mass of a certain volume of copper}}{\text{The mass of the same volume of water}}=8.9$
AnswerCorrect option: B. $=\frac{\text{The volume of a certain mass of copper}}{\text{The volume of the same mass of water}}=8.9$
This is because the density is defined as the ratio of the mass of the object to the volume of the object.
View full question & answer→MCQ 151 Mark
The weight of an object at the centre of the earth of radius $R$ is:
View full question & answer→MCQ 161 Mark
The mass of moon is about $0.012$ times that of earth and its diameter is about $0.25$ times that of earth. The value of $G$ on the moon will be:
- A
Less than that on the earth.
- B
More than that on the earth.
- ✓
Same as that on the earth.
- D
About one-sixth of that on the earth.
AnswerCorrect option: C. Same as that on the earth.
$G$ is universal gravitational constant. So, it remains constant everywhere.
View full question & answer→MCQ 171 Mark
The value of quantity $G$ in the formula for gravitational force:
- A
Depends on mass of the earth only.
- B
Depends on the radius of earth only.
- C
Depends on both mass and radius of earth.
- ✓
Depends neither on mass nor on radius of earth.
AnswerCorrect option: D. Depends neither on mass nor on radius of earth.
Because it is a constant in the formula for gravitational force.
View full question & answer→MCQ 181 Mark
The gravitational force of attraction between two objects is $x$. Keeping the masses of the objects unchanged, if the distance between the objects is halved, then the magnitude of gravitational force between them will become:
- A
$\frac{\text{x}}{4}$
- B
$\frac{\text{x}}{2}$
- C
$2\text{x}$
- ✓
$4\text{x}$
AnswerCorrect option: D. $4\text{x}$
$G = x$
$m_1$ and $m_2$ are constant
Since, $r$ is reduced to half, let, $\text{r} =\frac{\text{r}}{2}$
Gravitation force, $\text{F}=\text{G}\times\text{m}_1\times\frac{\text{m}_2}{\text{r}_2} = \text{x}$
When $r$ is reduced to half the force becomes, $\text{F}=\text{G}\times\text{m}_1\times\frac{\text{m}_2}{(\text{r})^2}$
$= \text{G}\times\text{m}_1\times\frac{\text{m}_2}{\Big(\frac{\text{r}}{2}\Big)^2}$
$= 4\text{x}$
View full question & answer→MCQ 191 Mark
According to one of the Kepler's laws of planetary motion:
- A
$\text{r}^2\propto\text{T}^3$
- B
$\text{r}\propto\text{T}^2$
- ✓
$\text{r}^3\propto\text{T}^2$
- D
$\text{r}^3\propto\frac{1}{\text{T}^2}$
AnswerCorrect option: C. $\text{r}^3\propto\text{T}^2$
According to Kepler’s third law of planetary motion, the cube of mean distance of a planet from the sun is directly proportional to the square of time it takes to move around the sun.
View full question & answer→MCQ 201 Mark
The diagrams represent four measuring cylinders containing liquids. The mass and volume of the liquid in each cylinder are stated. Which two measuring cylinders could contain an idential liquid?
- A
$W$ and $X$.
- B
$W$ and $Y$.
- C
$X$ and $Y$.
- ✓
$X$ and $Z$.
AnswerCorrect option: D. $X$ and $Z$.
This is because the density of these two liquids is same.
View full question & answer→MCQ 211 Mark
Four balls, $A, B, C$ and $D$ displace $10\ mL, 24\ mL, 15\ mL$ and $12\ mL$ of a liquid respectively, when immersed completely. The ball which will undergo the maximum apparent loss in weight will be:
AnswerThis is because $B$ has displaced maximum amount of water.
View full question & answer→MCQ 221 Mark
A rectangular wooden block has length, breadth and height of $50\ cm, 25\ cm$ and $10\ cm$, respectively. This wooden block is kept on ground in three different ways, turn by turn. Which of the following is the correct statement about the pressure exerted by this block on the ground?
- A
The maximum pressure is exerted when the length and breadth form the base.
- B
The maximum pressure is exerted when length and height form the base.
- ✓
The maximum pressure is exerted when breadth and height form the base.
- D
The minimum pressure is exerted when length and height form the base.
AnswerCorrect option: C. The maximum pressure is exerted when breadth and height form the base.
This is because the pressure is inversely proportional to the surface area.
View full question & answer→MCQ 231 Mark
The law of gravitation gives the gravitational force between:
- A
The earth and a point mass only.
- B
The earth and the sun only.
- ✓
Any two bodies having some mass.
- D
Any two charged bodies only.
AnswerCorrect option: C. Any two bodies having some mass.
Any two bodies having the same mass.
View full question & answer→MCQ 241 Mark
An object is put in three liquids having different densities, one by one. The object floats with $\frac{1}{9},\frac{2}{11}$ and $\frac{3}{7}$ parts of its volume outside the surface of liquids of densities $d_1, d_2$ and $d_3$ respectively. Which of the following is the correct order of the densities of the three liquids ?
- A
$d_1 > d2 > d_3$
- B
$d_2 > d_3 > d_1$
- ✓
$d_1 < d_2 < d_3$
- D
$d_3 > d_2 >d_1$
AnswerCorrect option: C. $d_1 < d_2 < d_3$
This is because if the density of the liquid is more than the object, then the object will float on the liquid. The more the object gets immersed in the liquid, lesser is the density of the liquid.
View full question & answer→