Govt. Exams
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Topics in JEE Physics
A rope can withstand maximum tension of 500 N. A mass of 40 kg is suspended and pulled horizontally. The maximum horizontal force is:
Correct Answer:
A. 300 N
EXPLANATION
Tension T = √[(mg)² + F²]. 500 = √[(400)² + F²]. F² = 250000 - 160000 = 90000. F = 300 N
A 2 kg mass moving at 3 m/s collides elastically with a 1 kg mass at rest. The velocity of 2 kg mass after collision is:
Correct Answer:
A. 1 m/s
EXPLANATION
For elastic collision: v₁ = [(m₁-m₂)u₁ + 2m₂u₂]/(m₁+m₂) = [(2-1)(3) + 0]/(3) = 1 m/s
A projectile is fired at 45° angle with initial velocity 40 m/s. The range is: (g = 10 m/s²)
Correct Answer:
C. 160 m
EXPLANATION
Range = u²sin(2θ)/g = (40²)sin(90°)/10 = 1600/10 = 160 m
A block of mass 5 kg is placed on a rough surface (μ = 0.2). The maximum static friction is:
Correct Answer:
C. 10 N
EXPLANATION
f_max = μ × N = μ × mg = 0.2 × 5 × 10 = 10 N (assuming g = 10 m/s²)
