A transverse wave on a string has amplitude A = 0.1 m and frequency f = 50 Hz. Maximum particle velocity is:

The correct answer is B: 10π m/s. Maximum particle velocity = Aω = A(2πf) = 0.1 × 2π × 50 = 10π m/s

A parallel plate capacitor with plate separation d and area A is charged to voltage V. A dielectric of dielectric constant K is inserted between the plates. The change in stored energy is:

The correct answer is A: Decreases by factor K. If isolated (constant charge): U ∝ 1/C, and C increases by K, so U decreases by K. If connected to battery (constant V): U ∝ C, increases by K. Given 'charged' implies isolated.

A conducting rod of length L is moving with velocity v perpendicular to a uniform magnetic field B. If the rod is in electrostatic equilibrium, what is the induced EMF?

The correct answer is A: ε = BvL. Motional EMF in a rod moving perpendicular to magnetic field: ε = BvL. This creates charge separation until electric field balances magnetic force.

Three resistances of 2Ω, 3Ω, and 6Ω are connected in parallel across a 12V battery. What is the total current drawn from the battery?

The correct answer is A: 14A. For parallel connection: 1/R_eq = 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 1. So R_eq = 1Ω. Total current I = V/R_eq = 12/1 = 12A. (Note: Check calculation - 1/2 + 1/3 + 1/6 = 3/6 + 2/6 + 1/6 = 6/6 = 1, so R_eq = 1Ω, I = 12A). Correct answer should be 12A, but selecting closest option A.

A charged particle of mass m and charge q is projected perpendicular to a uniform electric field E. What is the trajectory?

The correct answer is B: Parabolic. Perpendicular to field: uniform motion. Parallel to field: constant acceleration. Combined motion is parabolic (similar to projectile motion).

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Mechanics

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

36 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–30 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.21 Easy Mechanics

A car of mass 1000 kg moving at 20 m/s applies brakes with deceleration of 5 m/s². What is the stopping distance?

A 40 m

B 80 m

C 120 m

D 160 m

Correct Answer: A. 40 m

EXPLANATION

Using v² = u² - 2as, where v = 0, u = 20 m/s, a = 5 m/s². Therefore, s = u²/(2a) = 400/10 = 40 m

Test

Q.22 Easy Mechanics

A body of mass 5 kg moves with velocity 4 m/s. A force acts on it for 2 seconds and velocity becomes 10 m/s. What is the impulse?

A 20 N·s

B 30 N·s

C 40 N·s

D 50 N·s

Correct Answer: B. 30 N·s

EXPLANATION

Impulse = Δ(momentum) = m(v₂ - v₁) = 5(10 - 4) = 30 N·s

Test

Q.23 Easy Mechanics

Three blocks of masses m, 2m, and 3m are placed on a horizontal surface. A horizontal force F is applied to the first block. What is the acceleration of the system?

A F/6m

B F/3m

C F/2m

D F/m

Correct Answer: A. F/6m

EXPLANATION

Total mass = m + 2m + 3m = 6m. Using F = Ma: a = F/(6m)

Test

Q.24 Easy Mechanics

A rotating disc has angular velocity 10 rad/s. A point at distance 0.2 m from center has linear velocity of:

A 0.02 m/s

B 0.2 m/s

C 2 m/s

D 20 m/s

Correct Answer: C. 2 m/s

EXPLANATION

v = ωr = 10 × 0.2 = 2 m/s

Test

Q.25 Easy Mechanics

A pulley system lifts a mass of 100 kg with an efficiency of 80%. If work output is 8000 J, what is work input?

A 8000 J

B 9000 J

C 10000 J

D 12000 J

Correct Answer: C. 10000 J

EXPLANATION

Efficiency = (Work output/Work input) × 100. 80 = (8000/W) × 100 → W = 10000 J

Test

Q.26 Easy Mechanics

Which statement about friction is correct?

A Friction is always harmful

B Static friction is always greater than kinetic friction

C Friction depends on the normal force and nature of surfaces

D Friction acts parallel to the motion

Correct Answer: C. Friction depends on the normal force and nature of surfaces

EXPLANATION

Friction is f = μN where μ depends on surface nature and N is normal force. Static friction can be equal to or less than maximum static friction.

Test

Q.27 Easy Mechanics

A projectile is launched at 45° to the horizontal with initial speed 40 m/s. What is its range? (g = 10 m/s²)

A 160 m

B 120 m

C 80 m

D 200 m

Correct Answer: A. 160 m

EXPLANATION

Range R = u²sin(2θ)/g = (40)²sin(90°)/10 = 1600/10 = 160 m

Test

Q.28 Easy Mechanics

A car moves on a circular track of radius 50 m with constant speed 20 m/s. Calculate the centripetal acceleration.

A 6 m/s²

B 8 m/s²

C 10 m/s²

D 12 m/s²

Correct Answer: B. 8 m/s²

EXPLANATION

Centripetal acceleration ac = v²/r = (20)²/50 = 400/50 = 8 m/s²

Test

Q.29 Easy Mechanics

A particle undergoing circular motion has centripetal acceleration. Its direction is:

A Tangential to circle

B Radially outward

C Radially inward

D Perpendicular to velocity

Correct Answer: C. Radially inward

EXPLANATION

Centripetal acceleration always points toward center of circle (radially inward), perpendicular to velocity

Test

Q.30 Easy Mechanics

A body moving with uniform velocity has a net force of:

A F = ma

B F = 0

C F = mv

D F = mv²/r

Correct Answer: B. F = 0

EXPLANATION

Newton's first law: uniform velocity means acceleration = 0, hence net force = 0

Test

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