Recent questions and answers in jee-2018

A plane progressive wave of frequency 25 Hz, amplitude `2.5 xx 10^(-5)` m and initial phase zero moves along the negative x-direction with a velocity of 300 m`s^(-1)`. A and B are two points 6m apart on the iine of propagation of the wave. At any instant the phase difference between A and B is `theta`. The phase difference and path difference when the displacement of the particle at A and B is `triangle`, then

Transverse waves of same frequency are generated in two steel wires A and B. The diameters of A is twice of B and the tension in A is half that in B. The ratio of velocities of wave in A and B is

The vibrations of a string fixed at both ends are represented by `y=16Sin((pix)/15)Cos(96pit).`Where 'x' and 'y' are in cm and 't' in seconds. Then the phase difference between the points at x= 13 cm and x= 16 in radian is

A travelling wave represented by `y=Asin(omegat-kx)` is superimposed on another wave represented by `y = Asin(omegat + kx)` . The resultant is

The equation of displacement of two waves are given as `y_1=10 sin (3pit+pi/3); y_2=5[sin 3pit+sqrt3 cos 3pit]` then what is the ratio of their amplitudes

Two bodies of 6 kg and 4 kg masses have their velocity `5hati+2hatj-8hatk` and `10hati-2hatj+5hatk` respectively. Then the velocity of their centre of mass is

A body is thrown horizontally from the top of a tower of 5 m height. It touches the ground at a distance of 10 m from the foot of the tower. The initial velocity of the body is (Take g = 10 m`s^(–2)`)

Two cells of emf `epsilon_1` and `epsilon_2(epsilon_1>epsilon_2)` are connected as shown in figure. When a potentiometer is connected between A and B, the balancing length of the potentiometer wire is 300 cm. On connecting the same potentiometer between A and C, the balancing length is 100 cm. The ratio is `epsilon_1 : epsilon_2` is

In an experiment on photoelectric emission from a metallic surface, wavelength of incident light is `2×10^(–7)` m and stopping potential is 2.5 V. The threshold frequency of the metal is apparoximately (Charge of electron e = `1.6×10^(–19)` C, Planck's constant h =`6.6 × 10^(–34)` Js)

When a wire of length 10 m is subjected to a force of 100 N along its length, the lateral strain produced is `0.01×10^(–3)`. The Poisson's ratio was found to be 0.4. If the area of cross-section of wire is 0.025 `m^2`, Its Young's modulus is

A fork A has frequency 2% more than the standard fork and B has a frequency 3% less than the frequency of same standard fork. The forks A and B when sounded together produced 6 beats `s^(–1)`. The frequency of fork A is

You drive a car at a speed of 70 km `h^(–1)` in a straight road for 8.4 km and then the car runs out of petrol. You walk for 30 min to reach a petrol pump at a distance of 2 km. The average velocity from the beginning of your drive till you reach the petrol pump is

The far point of a near sighted person is 6.0 m from her eyes, and she wears contacts that enable her to see distant objects clearly. A tree is 18.0 m away and 2.0 m high. How high is the image formed by the contacts

Force on a 1 kg mass on earth of radius R is 10 N. Then the force on a satellite revolving around the earth in the mean orbital radius `(3R)/2` will be (mass of satellite is 100 kg)

The equation of a wave is represented by `Y=10^(-5) sin [100t -X/10]m`, then the velocity of wave will be

A mass of 0.2 kg is attached to the lower end of a masseless spring of force constant 200 N`m^(–1)`, the upper end of which is fixed to a rigid support. Which of the following statement is not true

On shining light of wavelength `6.2×10^(–6)` m on a metal surface photo-electrons are emiited. The work function of the metal is 0.1 eV. Find the kinetic energy of a photo-electron (in eV)

The half-life of a radioactive isotope X is 50 years. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1 : 15 in a sample of a given rack. The age of the rock was estimated to be

The diode used in a circuit shown in the figure has a constant voltage drop at 0.5 V at all currects and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with diode, for obtaining maximum current

A uniform chain of mass m and length `l` is lying on a table with `l/4` of its length hanging freely from the edge of the table. The amount of work done in dragging the chain on the table completely is

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