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Mechanics

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

36 Q 9 Topics Take Test
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Difficulty: All Easy Medium Hard 1–10 of 36
Topics in JEE Physics
Q.1 Easy Mechanics
An elevator accelerates upward at 2 m/s². A person of mass 60 kg stands in it. What is the normal force exerted by the floor on the person? (g = 10 m/s²)
A 600 N
B 660 N
C 720 N
D 540 N
Correct Answer:  C. 720 N
EXPLANATION

N - mg = ma (upward acceleration), so N = m(g + a) = 60(10 + 2) = 60 × 12 = 720 N

Test
Q.2 Easy Mechanics
A body of mass 2 kg moves in a circular path of radius 0.5 m with constant speed. If the centripetal acceleration is 8 m/s², what is the centripetal force required?
A 16 N
B 8 N
C 4 N
D 2 N
Correct Answer:  A. 16 N
EXPLANATION

Centripetal force F = ma_c = 2 × 8 = 16 N. This is the net force directed toward the center of circular motion.

Test
Q.3 Easy Mechanics
A projectile is launched at an angle of 45° with initial velocity 20 m/s. Neglecting air resistance, what is the maximum height reached? (g = 10 m/s²)
A 10 m
B 20 m
C 5 m
D 15 m
Correct Answer:  A. 10 m
EXPLANATION

At 45°, vertical component = 20sin(45°) = 10√2 m/s. Using v² = u² - 2gh, at max height v=0: h = u²/(2g) = (10√2)²/(2×10) = 200/20 = 10 m

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Q.4 Easy Mechanics
A particle undergoes SHM with amplitude A = 0.5 m and angular frequency ω = 4 rad/s. What is its maximum velocity?
A 1 m/s
B 2 m/s
C 4 m/s
D 8 m/s
Correct Answer:  B. 2 m/s
EXPLANATION

Maximum velocity in SHM = ωA = 4 × 0.5 = 2 m/s

Test
Q.5 Easy Mechanics
A particle experiences three forces: F₁ = 3i N, F₂ = 4j N, and F₃ = -3i - 4j N. What is the net force magnitude?
A 0 N
B 5 N
C 7 N
D 10 N
Correct Answer:  A. 0 N
EXPLANATION

Net force = (3-3)i + (4-4)j = 0i + 0j = 0 N. The magnitude is 0 N.

Test
Q.6 Easy Mechanics
A block slides down a frictionless incline of height 5 m. What is its speed at the bottom? (g = 10 m/s²)
A 5 m/s
B 10 m/s
C 15 m/s
D 20 m/s
Correct Answer:  B. 10 m/s
EXPLANATION

Using energy conservation: mgh = ½mv². v = √(2gh) = √(2×10×5) = √100 = 10 m/s

Test
Q.7 Easy Mechanics
What is the moment of inertia of a uniform disc of mass M and radius R about an axis perpendicular to the disc passing through its center?
A MR²
B ½MR²
C ⅓MR²
D ¼MR²
Correct Answer:  B. ½MR²
EXPLANATION

The moment of inertia of a uniform disc about its central perpendicular axis is I = ½MR²

Test
Q.8 Easy Mechanics
A particle moves with constant velocity v = 5 m/s in a circular path of radius 10 m. What is its centripetal acceleration?
A 0.5 m/s²
B 2 m/s²
C 2.5 m/s²
D 5 m/s²
Correct Answer:  C. 2.5 m/s²
EXPLANATION

Centripetal acceleration = v²/r = 25/10 = 2.5 m/s²

Test
Q.9 Easy Mechanics
A block of mass 5 kg is placed on a frictionless inclined plane at 30°. What is the acceleration down the plane? (g = 10 m/s²)
A 5 m/s²
B 8.66 m/s²
C 5√3 m/s²
D 2.5 m/s²
Correct Answer:  A. 5 m/s²
EXPLANATION

a = g sin(30°) = 10 × 0.5 = 5 m/s²

Test
Q.10 Easy Mechanics
A body is projected vertically upward with velocity 40 m/s. If g = 10 m/s², what is the maximum height reached?
A 40 m
B 80 m
C 160 m
D 20 m
Correct Answer:  B. 80 m
EXPLANATION

Using v² = u² - 2gh, at maximum height v = 0. So 0 = 1600 - 2(10)h, h = 80 m

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