JEE Main Practice Test- 7 - JEE MCQ

A balloon is moving upwards with a speed of 20 m/s. When it is at a height of 14 m from ground in front of a plane mirror in as shown in figure, a boy drops himself from the balloon. Find the time duration for which he will see the image of source S placed symmetrically before plane mirror during free fall.

Prism angle & refractive index for a prism are 60^o & 1.414. Angle of minimum deviation will be

If a gas is heated at constant pressure then what percentage of total heat supplied is used for doing work ? (Given : γ for gas = 4/3)

Four persons K, L, M, N are initially at the four corners of a square of side d. Each person now moves with a uniform speed  v in such a way that K always moves directly towards L, L directly towards M, M directly towards N, and N directly towards K. The four persons will meet at a time .....

Estimate the speed of sound in air at standard temperature and pressure. The mass of 1 mole of air is 29.0 × 10^-3 kg

A pendulum bob is suspended on a flat car that moves with velocity v₀. The flat car is stopped by a bumper
(i) What is the angle through which the pendulum swings.
(ii) If the swing angle is θ = 60° and l = 10m, what was the initial speed of the flat car?

Two slits, 4 mm apart, are illuminated by light of wavelength 6000Å. What will be the fringe width on a screen placed 2 m from the slits?

A car moves uniformly along a horizontal sine curve y = a sin (x/α), where a and α are certain constants. The coefficient of friction between the wheels and the road is equal to k. At what velocity will the car ride without sliding?

A large tank filled with water to a height 'h' is to be emptied through a small hole at the bottom. The ratio of times taken for the level of water to fall from h to h/2 and from h/2 to zero is

A bullet of mass 2 g is having a charge of 2μC. The potential difference it must be accelerated through, starting from rest, to acquire a speed of 10 m/s is

A wire of length L and 3 identical cells of negligible internal resistance are connected in series. Due to the current, the temperature of the wire is raised by ΔT in a time t. A number of N similar cells are now connected in series with a wire of the same material and area of cross-section but of length 2L. The temperature of the wire is raised by the same amount ΔT in the same time . The value of N is

The intensity of the light coming from one of the slits in YDSE is double the intensity from the other slit. Find the ratio of maximum intensity to minimum intensity in the interference fringe pattern observed.

Consider α-particles, β-particles and γ- rays each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are

A battery is supplying power to a tape-recorder by cable of resistance of 0.02 Ω . If the battery is generating 50 W power at 5V, then power received by tape-recorder is :

A uniform rod of mass m and length ℓ is rotating with constant angular velocity ω about an axis which passes through its one end and perpendicular to the length of rod. The area of cross section of the rod is A and its Young's modulus is Y. Neglect gravity. The strain at the mid point of the rod is :

Initially car A is 10.5 m ahead of car B. Both start moving at time t = 0 in the same direction along a straight line. The velocity time graph of two cars is shown in figure. The time when the car B will catch the car A, will be ;

Two masses m₁ and m₂ are connected by a string of length l. They are held in a horizontal plane at a height H above two heavy plates A and B made of different material placed on the floor. Initially distance between two masses is a < l. When the masses are released under gravity they make collision with A and B co - efficient of restitution 0.8 and 0.4 respectively. The time after the collision when the string becomes tight is

The difference between (n + 2)^th Bohr radius and n^th Bohr radius is equal to the (n – 2)^th Bohr radius. The value of n is ?

The figure shows an RC circuit with a parallel plate capacitor. Before switching on the circuit, plate A of the capacitor has a charge –Q₀ while plate B has no net charge. Now, at t = 0, the circuit is switched on. How much time (in second) will elapse before the net charge on plate A becomes zero.

(GivenC=1μF, Q₀=1mC, ε=1000V and 

A thin non conducting disc of mass M = 2kg, charge Q = 2x10^–2 C and radius R = 1/6m is placed on a frictionless horizontal plane with its centre at the origin of the coordinate system. A non uniform, radial magnetic field  exists in space, where B₀ = 10T and  is a unit vector in the radially outward direction. The disc is set in motion with an angular velocity w = x*10² rad/sec, about an axis passing through its centre and perpendicular to its plane, as shown in the figure. At what value of x, the disc will lift off from the surface.

All springs, string and pulley shown in figure are light. Initially when both the springs were in their natural state, the system was released from rest. The maximum displacement of block m is  calculate x

In Young’s Double slit experiment, a thin glass mica strip of thickness (t = 8λ) is pasted infront of slit S₁. If the same strip is now shifted in front of other slit S₂. If the number of fringes which will cross the central point on the screen is N. Find N? (d >> D, λ << d and n_mica = 1.5)

A saturated aqueous solution of sparingly soluble salt AB₃ has the vapour pressure 0.08 mm lesser than the vapour pressure 17.33 mm of solvent at 25^oC. The solubility product of AB₃ is :

Photoelectric emission is observed from a surface for frequencies v₁ and v₂ of the incident radiation (v₁ > v₂). If the maximum kinetic energies of the photoelectrons in the two cases are in the ration l : k then the threshold frequency v₀ is given by :

In the following electron dot structure calculate the formal charge from left to right nitrogen atom ?

A 50 litre vessel is equally divided into three parts with the help of two stationary semi permeable membrane (SPM). The vessel contains 60 g H₂ gas in the left chamber, 160 g O₂ in the middle and 140 g N₂ in the right one. The left SPM allows transfer of only H₂ gas while the right one allows the transfer of both H₂ and N₂. The final ratio of pressure in the three chambers.

Acetamide is treated separately with the following reagents. Which of these would give methylamine ?