Other Physics · JEE Main previous year questions

A car is standing 200 m behind a bus, which is also at rest. The two start moving at the same instant but with different forward accelerations. The bus has acceleration $2m/{\mathrm{s}}^2$ and the car has acceleration $4m/{\mathrm{s}}^2$ . The car will catch up with the bus after a time of :

1. A.$\sqrt{110}s$
2. B.$\sqrt{120}s$
3. C.$10\sqrt{2}s$
4. D.$15\mathrm{s}$

Imagine that a reactor converts all given mass into energy and that it operates at a power level of $10^9\mathrm{watt}$. The mass of the fuel consumed per hour in the reactor will be : (velocity of light, c is $3\times 10^{8}m/s$)

1. A.$0.96\mathrm{gm}$
2. B.$0.8\mathrm{gm}$
3. C.$4\times 10^{-2}\mathrm{gm}$
4. D.$6.6\times 10^{-5}\mathrm{gm}$

1. A.
2. B.
3. C.
4. D.

1. A.
2. B.
3. C.
4. D.

In a physical balance working on the principle of moments, when 5 mg weight is placed on the left pan, the beam becomes horizontal. Both the empty pans of the balance are of equal mass. Which of the following statements is correct ?

1. A.Left arm is longer than the right arm
2. B.Both the arms are of same length
3. C.Left arm is shorter than the right arm
4. D.Every object that is weighed using this balance appears lighter than its actual weight.

The maximum velocity of the photoelectrons emitted from the surface is v when light of frequency n falls on a metal surface. If the incident frequency is increased to 3n, the maximum velocity of the ejected photoelectrons will be :

1. A.less than $\sqrt{3}\mathrm{v}$
2. B.$\mathrm{v}$
3. C.more than $\sqrt{3}v$
4. D.equal to $\sqrt{3}v$

A pipe open at both ends has a fundamental frequency $f$ in air. The pipe is dipped vertically in water so that half of it is in water. The fundamental frequency of the air column is now :

1. A.$2f$
2. B.$f$
3. C.$\frac{f}{2}$
4. D.$\frac{3f}{4}$

1. A.$OR$
2. B.$NAND$
3. C.$NOT$
4. D.$AND$

For a common emitter configuration, if $\alpha$ and $\beta$ have their usual meanings, the incorrect relationship between $\alpha$ and $\beta$ is :

1. A.$\alpha =\frac{\beta }{1+\beta }$
2. B.$\alpha =\frac{{\beta }^2}{1+{\beta }^2}$
3. C.$\frac{1}{\alpha }=\frac{1}{\beta }+1$
4. D.$\alpha =\frac{\beta }{1-{\beta }^2}$

Choose the correct statement :

1. A.In amplitude modulation the amplitude of the high frequency carrier wave is make to vary in proportion to the amplitude of the audio signal.
2. B.In amplitude modulation the frequency of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
3. C.In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal.
4. D.In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the frequency of the audio signal.

Assuming human pupil to have a radius of $0.25\mathrm{cm}$ and a comfortable viewing distance of $25\mathrm{cm}$, the minimum separation between two objects that human eye can resolve at $500\mathrm{nm}$ wavelength is :

1. A.$100\mu \mathrm{m}$
2. B.$300\mu \mathrm{m}$
3. C.$1\mu \mathrm{m}$
4. D.$30\mu \mathrm{m}$

1. A.Depends on $H$
2. B.$1:1$
3. C.$2:2$
4. D.$1:2$

The disturbance $y(x,t)$ of a wave propagating in the positive $x$-direction is given by $y=\frac{1}{1+x^2}$ at time $t=0$ and by $y=\frac{1}{[1+(x-1{)}^2]}$ at $t=2\mathrm{s}$, where $x$ and $y$ are in meters. The shape of the wave disturbance does not change during the propagation. The velocity of wave in $m/s$ is

1. A.$2.0$
2. B.$4.0$
3. C.$0.5$
4. D.$1.0$

Photoelectrons are ejected from a metal when light of frequency $\nu$ falls on it. Pick out the wrong statement from the following.

1. A.No electrons are emitted if $\nu$ is less than $W/h$, where $W$ is the work function of the metal
2. B.The ejection of the photoelectrons is instantaneous.
3. C.The maximum energy of the photoelectrons is $h\nu$.
4. D.The maximum energy of the photoelectrons is independent of the intensity of the light.

Assuming the earth to be a sphere of uniform density, the acceleration due to gravity inside the earth at a distance of $r$ from the centre is proportional to

1. A.$r$
2. B.$r^{-1}$
3. C.$r^2$
4. D.$r^{-2}$

Which of the following Statements is correct?

1. A.The rate of radioactive decay cannot be controlled but that of nuclear fission can be controlled.
2. B.Nuclear forces are short range, attractive and charge dependent.
3. C.Nuclei of atoms having same number of neutrons are known as isobars.
4. D.Wavelength of matter waves is given by de Broglie formula but that of photons is not given by the same formula

A car of mass $1000\mathrm{kg}$ is moving at a speed of $30m/s$. Brakes are applied to bring the car to rest. If the net retarding force is $5000\mathrm{N}$, the car comes to stop after travelling $d\mathrm{m}$ in $t\mathrm{s}$. Then

1. A.$d=150$, $t=5$
2. B.$d=120$, $t=8$
3. C.$d=180$, $t=6$
4. D.$d=90$, $t=6$

An engine pumps water continuously through a hose. Water leaves the hose with velocity $v$ and $m$ is mass per unit length of the water jet. If this jet hits a surface and came to rest instantaneously, the force on the surface is

1. A.$m{v}^3$
2. B.$m{v}^2$
3. C.$\frac{1}{2}m{v}^2$
4. D.$\frac{1}{2}m{v}^3$

1. A.
2. B.
3. C.
4. D.

1. A.$OA$
2. B.$OC$
3. C.$OD$
4. D.$OB$

1. A.$\frac{\ell }{\sqrt{2\pi }}$
2. B.$\frac{\ell }{\sqrt{3\pi }}$
3. C.$\frac{\ell }{3\pi }$
4. D.$\frac{\ell }{2\pi }$

The heat radiated per unit area in 1 hour by a furnace whose temperature is $3000\mathrm{K}$ is ($\sigma =5.7\times 10^{-8}\mathrm{W}{\mathrm{m}}^{-2}{\mathrm{K}}^{-4}$)

1. A.$1.7\times 10^{10}\mathrm{J}$
2. B.$1.1\times 10^{12}\mathrm{J}$
3. C.$2.8\times 10^8\mathrm{J}$
4. D.$4.6\times 10^6\mathrm{J}$

1. A.
2. B.
3. C.
4. D.

1. A.OR gate
2. B.NOT gate
3. C.XOR gate
4. D.NAND gate

A particle has an initial velocity $3\hat{i}+4\hat{j}$ and an acceleration of $0.4\hat{i}+0.3\hat{j}$. Its speed after 10 s is:

1. A.$7\sqrt{2}\mathrm{units}$
2. B.$7\mathrm{units}$
3. C.$8.5\mathrm{units}$
4. D.$10\mathrm{units}$