A block is pushed up an incline of angle 30° with initial velocity 10 m/s. If coefficient of kinetic friction is 0.2, how far will it travel before stopping? (g = 10 m/s²)

The correct answer is A: 3.2 m. Deceleration a = g(sinθ + μcosθ) = 10(0.5 + 0.2×0.866) = 10(0.5 + 0.173) = 6.73 m/s². Using v² = u² - 2as: 0 = 100 - 2(6.73)s, s ≈ 3.2 m

In a MOSFET, the threshold voltage VT is defined as the gate voltage at which:

The correct answer is B: Inversion layer just forms at the oxide-semiconductor interface. Threshold voltage VT is when the surface band bending creates an inversion layer, transition from depletion to strong inversion.

A point charge q is placed at distance r from an infinite grounded conducting plane. The force on the charge is:

The correct answer is A: F = q²/(16πε₀r²). By method of images, image charge -q is at distance r behind plane. Total distance = 2r. F = kq²/(2r)² = q²/(16πε₀r²)

A heat engine absorbs 1000 J from a hot reservoir and rejects 600 J to a cold reservoir in one cycle. Its efficiency is:

The correct answer is A: 40%. Efficiency η = W/Q_h = (Q_h − Q_c)/Q_h = (1000 − 600)/1000 = 400/1000 = 0.40 = 40%

A biconvex lens (n = 1.5) has both radii of curvature equal to 20 cm. What is its focal length?

The correct answer is B: 20 cm. Using lens maker's formula: 1/f = (n-1)[1/R₁ + 1/R₂] = (0.5)[1/20 + 1/20] = (0.5)(2/20) = 1/20. Therefore f = 20 cm.

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JEE Physics

Physics questions for JEE Main — Mechanics, Electrostatics, Optics, Modern Physics.

301 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 301

Topics in JEE Physics

All Mechanics 100 Thermodynamics 100 Electrostatics 100 Current Electricity 100 Magnetism 100 Optics 100 Modern Physics 100 Semiconductors 100 Waves 100

Q.1 Easy Waves

A transverse wave travels along a stretched string with equation y = 0.02sin(50πt - 4πx), where x and y are in meters and t is in seconds. What is the wave velocity and wavelength of this wave?

A v = 12.5 m/s, λ = 0.5 m

B v = 6.25 m/s, λ = 1 m

C v = 25 m/s, λ = 0.25 m

D v = 12.5 m/s, λ = 1 m

Correct Answer: A. v = 12.5 m/s, λ = 0.5 m

EXPLANATION

From y = 0.02sin(50πt - 4πx), comparing with y = Asin(ωt - kx): ω = 50π rad/s, k = 4π rad/m. Wavelength λ = 2π/k = 2π/(4π) = 0.5 m. Wave velocity v = ω/k = 50π/(4π) = 12.5 m/s.

Test

Q.2 Easy Waves

A wave traveling in the positive x-direction reflects from a fixed end. What is the phase change upon reflection?

A 0°

B 90°

C 180°

D 270°

Correct Answer: C. 180°

EXPLANATION

When a wave reflects from a fixed (denser) end, it undergoes a phase change of π radians or 180°

Test

Q.3 Easy Waves

Two sources produce sound waves of frequencies 250 Hz and 254 Hz. What is the beat frequency heard?

A 2 Hz

B 4 Hz

C 6 Hz

D 254 Hz

Correct Answer: B. 4 Hz

EXPLANATION

Beat frequency = |f₁ - f₂| = |250 - 254| = 4 Hz

Test

Q.4 Easy Waves

A string is vibrating in its second harmonic with frequency 200 Hz. What is the fundamental frequency?

A 100 Hz

B 200 Hz

C 300 Hz

D 400 Hz

Correct Answer: A. 100 Hz

EXPLANATION

In the second harmonic (n=2), f₂ = 2f₁. Therefore, f₁ = f₂/2 = 200/2 = 100 Hz

Test

Q.5 Easy Waves

Two waves of same frequency interfere constructively. If individual amplitudes are 3 cm and 4 cm, what is the resultant amplitude?

A 1 cm

B 5 cm

C 7 cm

D 3.5 cm

Correct Answer: C. 7 cm

EXPLANATION

For constructive interference, A_resultant = A₁ + A₂ = 3 + 4 = 7 cm

Test

Q.6 Easy Waves

The amplitude of a wave is doubled. How does this affect the intensity of the wave?

A Intensity is doubled

B Intensity is quadrupled

C Intensity remains the same

D Intensity is halved

Correct Answer: B. Intensity is quadrupled

EXPLANATION

Intensity is proportional to the square of amplitude (I ∝ A²). When A becomes 2A, I becomes 4I

Test

Q.7 Easy Waves

A guitar string of length 0.6 m is vibrating in its third harmonic. How many antinodes are present on the string?

A 1

B 2

C 3

D 4

Correct Answer: C. 3

EXPLANATION

In the nth harmonic, the number of antinodes equals n. For the third harmonic (n=3), there are 3 antinodes

Test

Q.8 Easy Waves

Which of the following correctly represents the relationship between wave velocity, frequency, and wavelength?

A v = f/λ

B v = fλ

C v = λ/f

D v = f + λ

Correct Answer: B. v = fλ

EXPLANATION

The fundamental wave equation is v = fλ, where v is velocity, f is frequency, and λ is wavelength

Test

Q.9 Easy Waves

A wave is traveling through a medium with velocity v = 340 m/s. If the wavelength is 0.85 m, what is the frequency of the wave?

A 400 Hz

B 289.25 Hz

C 400 Hz

D 100 Hz

Correct Answer: A. 400 Hz

EXPLANATION

Using v = fλ, f = v/λ = 340/0.85 = 400 Hz

Test

Q.10 Easy Waves

The Doppler effect is observed when:

A Wave amplitude changes

B Relative motion exists between source and observer

C Wave encounters a barrier

D Wavelength remains constant

Correct Answer: B. Relative motion exists between source and observer

EXPLANATION

Doppler effect occurs due to relative motion between source and observer, causing apparent frequency change

Test

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