Other Physics · JEE Main previous year questions

The height at which the acceleration due to gravity becomes $\frac{g}{9}$ (where $g=$ the acceleration due to gravity on the surface of the earth) in terms of $R$, the radius of the earth, is:

1. A.$\frac{R}{\sqrt{2}}$
2. B.$R/2$
3. C.$\sqrt{2}R$
4. D.$2R$

Two wires are made of the same material and have the same volume. However wire 1 has cross-sectional area $A$ and wire 2 has cross-sectional area $3A$. If the length of wire 1 increases by $\Delta x$ on applying force $F$, how much force is needed to stretch wire 2 by the same amount?

1. A.$4F$
2. B.$6F$
3. C.$9F$
4. D.$F$

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

1. A.The forces on $AD$ are $BC$ are zero.
2. B.The magnitude of the net force on the loop is given by $\frac{I_{1}I}{4\pi }{\mu }_0[2(b-a)+\pi /3(a+b)]$.
3. C.The magnitude of the net force on the loop is given by $\frac{{\mu }_{0}I{I}_1}{24ab}(b-a)$.
4. D.The forces on $AB$ and $DC$ are zero.

A player caught a cricket ball of mass $150g$ moving at a rate of $20m/s$. If the catching process is completed in $0.1s$, the force of the blow exerted by the ball on the hand of the player is equal to

1. A.$150N$
2. B.$3N$
3. C.$30N$
4. D.$300N$

Two insulating plates are both uniformly charged in such a way that the potential difference between them is $V_2-V_1=20\mathrm{V}$. (i.e., plate 2 is at a higher potential). The plates are separated by $d=0.1\mathrm{m}$ and can be treated as infinitely large. An electron is released from rest on the inner surface of plate 1. What is its speed when it hits plate 2? $(e=1.6\times 10^{-19}\mathrm{C},m_e=9.11\times 10^{-31}\mathrm{kg})$

1. A.$2.65\times 10^{6}m/s$
2. B.$7.02\times 10^{12}m/s$
3. C.$1.87\times 10^{6}m/s$
4. D.$32\times 10^{-19}m/s$

A thermocouple is made from two metals, Antimony and Bismuth. If one junction of the couple is kept hot and the other is kept cold, then, an electric current will

1. A.flow from Antimony to Bismuth at the hot junction
2. B.flow from Bismuth to Antimony at the cold junction
3. C.not flow through the thermocouple
4. D.flow from Antimony to Bismuth at the cold junction

An electric bulb is rated 220 volt - 100 watt. The power consumed by it when operated on 110 volt will be

1. A.$75\mathrm{watt}$
2. B.$40\mathrm{watt}$
3. C.$25\mathrm{Watt}$
4. D.$50\mathrm{Watt}$

1. A.$0.33\mathrm{A}$
2. B.$0.5\mathrm{A}$
3. C.$0.67\mathrm{A}$
4. D.$0.17\mathrm{A}$

The flux linked with a coil at any instant '$t$' is given by $\varphi =10t^2-50t+250$ The induced $emf$ at $t=3\mathrm{s}$ is

1. A.$-190\mathrm{V}$
2. B.$-10\mathrm{V}$
3. C.$10\mathrm{V}$
4. D.$190\mathrm{V}$

A solid which is not transparent to visible light and whose conductivity increases with temperature is formed by

1. A.Ionic bonding
2. B.Covalent bonding
3. C.Vander Waals bonding
4. D.Metallic bonding

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

A car starting from rest accelerates at the rate $f$ through a distance $S$, then continues at constant speed for time $t$ and then decelerates at the rate $\frac{f}{2}$ to come to rest. If the total distance traversed is $15S$, then

1. A.$S=\frac{1}{6}f{t}^2$
2. B.$S=ft$
3. C.$S=\frac{1}{4}f{t}^2$
4. D.$S=\frac{1}{72}f{t}^2$

The relation between time $t$ and distance $x$ is $t=a{x}^2+bx$ where $a$ and $b$ are constants. The acceleration is

1. A.$2b{v}^3$
2. B.$-2ab{v}^2$
3. C.$2a{v}^2$
4. D.$-2a{v}^3$

A smooth block is released at rest on a $45^{\circ }$ incline and then slides a distance '$d$'. The time taken to slide is '$n$' times as much to slide on rough incline than on a smooth incline. The coefficient of friction is

1. A.${\mu }_k=\sqrt{1-\frac{1}{n^2}}$
2. B.${\mu }_k=1-\frac{1}{n^2}$
3. C.${\mu }_s=\sqrt{1-\frac{1}{n^2}}$
4. D.${\mu }_s=1-\frac{1}{n^2}$

A particle of mass $0.3\mathrm{kg}$ subjected to a force $F=-kx$ with $k=15N/m$. What will be its initial acceleration if it is released from a point $20\mathrm{cm}$ away from the origin?

1. A.$15m/{\mathrm{s}}^2$
2. B.$3m/{\mathrm{s}}^2$
3. C.$10m/{\mathrm{s}}^2$
4. D.$5m/{\mathrm{s}}^2$

Consider a car moving on a straight road with a speed of $100m/s$. The distance at which car can be stopped is $[{\mu }_k=0.5]$

1. A.$1000\mathrm{m}$
2. B.$800\mathrm{m}$
3. C.$400\mathrm{m}$
4. D.$100\mathrm{m}$

A spherical ball of mass $20\mathrm{kg}$ is stationary at the top of a hill of height $100\mathrm{m}$. It rolls down a smooth surface to the ground, then climbs up another hill of height $30\mathrm{m}$ and finally rolls down to a horizontal base at a height of $20\mathrm{m}$ above the ground. The velocity attained by the ball is

1. A.$20m/s$
2. B.$40m/s$
3. C.$10\sqrt{30}m/s$
4. D.$10m/s$

Average density of the earth

1. A.is a complex function of $g$
2. B.does not depend on $g$
3. C.is inversely proportional to $g$
4. D.is directly proportional to $g$

A gaseous mixture consists of $16\mathrm{g}$ of helium and $16\mathrm{g}$ of oxygen. The ratio $\frac{C_p}{C_v}$ of the mixture is

1. A.$1.62$
2. B.$1.59$
3. C.$1.54$
4. D.$1.4$

1. A.$\ln \left(\frac{r_2}{r_1}\right)$
2. B.$\frac{(r_2-r_1)}{(r_1{r}_2)}$
3. C.$(r_2-r_1)$
4. D.$\frac{r_1{r}_2}{(r_2-r_1)}$

1. A.relation between $\Delta U_1$ and $\Delta U_2$ can not be determined
2. B.$\Delta U_1=\Delta U_2$
3. C.$\Delta U_2<\Delta U_1$
4. D.$\Delta U_2>\Delta U_1$

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

The function ${\sin }^2(\omega t)$ represents

1. A.a periodic, but not $SHM$ with a period $\frac{\pi }{\omega }$
2. B.a periodic, but not $SHM$ with a period $\frac{2\pi }{\omega }$
3. C.a $SHM$ with a period $\frac{\pi }{\omega }$
4. D.a $SHM$ with a period $\frac{2\pi }{\omega }$

Two thin, long, parallel wires, separated by a distance '$d$' carry a current of '$i$' $A$ in the same direction. They will

1. A.repel each other with a force of ${\mu }_0{i}^2/(2\pi d)$
2. B.attract each other with a force of ${\mu }_0{i}^2/(2\pi d)$
3. C.repel each other with a force of ${\mu }_0{i}^2/(2\pi d^2)$
4. D.attract each other with a force of ${\mu }_0{i}^2/(2\pi d^2)$