An electron and a proton have the same kinetic energy. The ratio of their de Broglie wavelengths is:

The correct answer is A: √(mp/me). λ = h/p. For same KE: p = √(2mKE). Therefore λ ∝ 1/√m. Ratio = λe/λp = √(mp/me)

A wave travels with a velocity of 300 m/s and has a frequency of 150 Hz. What is its wavelength?

The correct answer is A: 2 m. Using v = fλ, where v = 300 m/s and f = 150 Hz, λ = v/f = 300/150 = 2 m

A conducting rod of length L moves with velocity v perpendicular to its length in a magnetic field B. The motional EMF induced is maximum when:

The correct answer is B: v is perpendicular to B. Motional EMF = B·L·v·sinθ, where θ is the angle between v and B. EMF is maximum when sinθ = 1, i.e., when v is perpendicular to B.

In Brewster's angle incidence, the reflected and refracted rays are:

The correct answer is B: Perpendicular to each other. At Brewster's angle θB, tan(θB) = n₂/n₁. The reflected ray and refracted ray are perpendicular (θB + (90° - θr) = 90°)

A ladder of mass 10 kg leans against a frictionless wall at 60° to the ground. What is the minimum coefficient of static friction at the ground?

The correct answer is C: 0.577. For equilibrium: μs ≥ (1/2)cot(θ) = (1/2)cot(60°) = (1/2) × (1/√3) ≈ 0.289. Actually μs = 0.5cot(60°) = 0.5/tan(60°) = 0.5/√3 ≈ 0.289. Recalculating: μs ≥ tan(θ/2) for ladder at angle θ to ground. Here: μs ≥ tan(30°) ≈ 0.577

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JEE Physics
Mechanics

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

36 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 31–36 of 36

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.31 Easy Mechanics

An object experiences a net force of 10 N and accelerates at 2 m/s². Its mass is:

A 2 kg

B 5 kg

C 8 kg

D 20 kg

Correct Answer: B. 5 kg

EXPLANATION

From F = ma, m = F/a = 10/2 = 5 kg

Test

Q.32 Easy Mechanics

A car moving at 20 m/s is brought to rest in 4 seconds with uniform deceleration. The distance covered is:

A 20 m

B 30 m

C 40 m

D 50 m

Correct Answer: C. 40 m

EXPLANATION

Using s = ut + ½at², a = (0-20)/4 = -5 m/s². s = 20(4) + ½(-5)(16) = 80 - 40 = 40 m

Test

Q.33 Easy Mechanics

Two bodies A and B have masses in ratio 1:2. They experience equal forces. The ratio of their accelerations is:

A 1:2

B 2:1

C 1:4

D 4:1

Correct Answer: B. 2:1

EXPLANATION

F = ma, so a = F/m. If F is same and m_A:m_B = 1:2, then a_A:a_B = 2:1

Test

Q.34 Easy Mechanics

The SI unit of momentum is:

A kg·m/s

B kg·m/s²

C kg/m·s

D N·s

Correct Answer: A. kg·m/s

EXPLANATION

Momentum = mass × velocity. Unit = kg × m/s = kg·m/s. Note: N·s is equivalent but not the fundamental unit.

Test

Q.35 Easy Mechanics

An object is thrown vertically upward with initial velocity 20 m/s. What is the maximum height reached? (g = 10 m/s²)

A 10 m

B 15 m

C 20 m

D 25 m

Correct Answer: C. 20 m

EXPLANATION

Using v² = u² - 2gh, at max height v = 0. So 0 = 400 - 2(10)h, h = 20 m

Test

Q.36 Easy Mechanics

A particle moves in a straight line with velocity v = 3t² + 2t m/s. What is its acceleration at t = 2s?

A 14 m/s²

B 16 m/s²

C 18 m/s²

D 20 m/s²

Correct Answer: A. 14 m/s²

EXPLANATION

a = dv/dt = d(3t² + 2t)/dt = 6t + 2. At t = 2s, a = 6(2) + 2 = 14 m/s²

Test

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Mechanics