2 Marks Questions

Question 12 Marks

An astronaut inside a small space ship orbiting around the earth cannot detect gravity. If the space station orbiting around the earth has a large size, can he hope to detect gravity?

Answer

Yes,
If the spaceship is large enough then the astronaut will definitely detect the Earth's gravity as Gravitational Force on the spaceship is directly proportional to the mass of spaceship so as a mass of bigger spaceship will be large and hence it will experience a noticeable amount of force which can be detected, we know gravitational force on a body is given as
$
F=\frac{Gm_1 m_2}{r^2}
$
Where, F is the gravitational force
G is the universal gravitational Constant
$m _1$ is mass of first body which in this case is earth
$m _2$ is the mass of second body which is the spaceship
and $r$ is the distance between earth and spaceship
so as the mass of spaceship $m _2$ increases the gravitational force experienced by it increases and hence can be detected i.e. Gravity can be detected.

View full question & answer→

Question 22 Marks

The mass of a bicycle rider along with the bicycle is 100 kg . He wants to cross over a circular turn of radius 100 m with a speed of $10 ms^{-1}$. If the coefficient of friction between the tyres and the road is 0.6 , will the rider be able to cross the turn? Take $g =10 ms^{-2}$.

Answer

The centripetal force acting on the bicycle is given by,
$
\begin{aligned}
& F_{C}=\frac{m v^2}{r} \\
& =\frac{100 \times 10 \times 10}{100} \\
& =100 N
\end{aligned}
$

View full question & answer→

Question 32 Marks

A small spherical ball of radius r falls with velocity v through a liquid having coefficient of viscosity $\eta$. Find the viscous drag F on the ball assuming it depends on $\eta, r$ and v . Take $K =6 \pi$.

Answer

Let $F =K \eta^a r^b v^c$, then
$
\begin{aligned}
& M^1 L^1 T^{-2}=\left[ML^{-1} T^{-1}\right]^{a}[L]^{b}\left[LT^{-1}\right]^{c} \\
& =M^{a} L^{-a+b+c} T^{-a-c} \\
& \therefore a=1,-a+b+c=1,-a-c=-2
\end{aligned}
$
On solving, $a = b = c =1$
Hence $F =K \eta r v=6 \pi \eta r v$ (Stoke's law)

View full question & answer→

Question 42 Marks

In CGS system, the value of Stefan's constant is $\sigma=5.67 \times 10^{-5} erg s ^{-1} cm^{-2} K^{-4}$. Find its value in SI units. Given $1 J=10^7 erg$.

Answer

In CGS system, $\sigma=5.67 \times 10^{-5} erg s ^{-1} cm^{-2} K^{-4}$. The SI unit of work is joule. We have,
$1 erg =10^{-7} J$ and $1 cm=10^{-2} m$
$\therefore$ The value of Stefan's constant in SI units is
$
\begin{aligned}
& \sigma=5.67 \times 10^{-5}\left[10^{-7} J\right] s^{-1}\left[10^{-2} m\right]^{-2} 2 K^{-4} \\
& =5.67 \times 10^{-5} \times 10^{-7} \times 10^4 Js^{-1} m^{-2} K^{-4} \\
& =5.67 \times 10^{-8} Js^{-1} m^{-2} K^{-4}
\end{aligned}
$

View full question & answer→

Question 52 Marks

If earth has a mass 9 times and radius twice that of a planet Mars, calculate the minimum velocity required by a rocket to pull out of the gravitational force of Mars. Take the escape velocity on the surface of earth to be 11.2 $kms ^{-1}$.

Answer

Here, $M_e=9 M_m$, and $R_e=2 R_m$
$v _{ e }$ (escape speed on surface of Earth) $=11.2 km / s$
Let $V_m$ be the speed required to pull out of the gravitational force of mars.
We know that
$
v_{e}=\sqrt{\frac{2 G M_e}{R_e}} \text { and } v_m=\sqrt{\frac{2 G M_m}{R_m}}
$
Dividing, we get $\frac{v_m}{v_e}=\sqrt{\frac{2 G M_m}{R_m} \times \frac{R_e}{2 G M_e}}$
$
\begin{aligned}
& =\sqrt{\frac{M_m}{M_e} \times \frac{R_e}{R_m}}=\sqrt{\frac{1}{9} \times 2}=\frac{\sqrt{2}}{3} \\
& \Rightarrow v_m=\frac{\sqrt{2}}{3}(11.2 km / s)=5.3 km / s
\end{aligned}
$

View full question & answer→

Question 62 Marks

What are longitudinal waves? Give examples too.

Answer

Longitudinal waves are the waves in which medium particles vibrate to and fro about their mean positions along a straight line parallel to the direction of wave propagation. In a longitudinal wave, each particle of matter vibrates about its normal rest position and along the axis of propagation, and all particles participating in the wave motion behave in the same manner, except that there is a progressive change in phase of vibration-i.e.,each particle completes its cycle of reaction at a later time. The combined motions result in the advance of alternating regions of compression and rarefaction in the direction of propagation. Waves setup in springs, waves set up in air columns (organ pipes), sound waves, transfer of motion from the engine to last bogey (or wagon) in a train etc., are common examples of longitudinal waves.

View full question & answer→

Physics 2 Marks Questions

Take a timed test