A stone tied to a string is whirled in a circle. The work done by tension in string is
A. Negative
B. Zero
C. Variable
D. Positive
Answer: Option B
Solution (By JKExamLibrary)
Tension is towards centre, displacement is tangential (velocity). Force perpendicular to displacement, cos90°=0, work zero. Centripetal force does no work, doesn't change speed.
Explanation:
Fuse wire made of alloy of tin and lead (or copper with low melting point). It has low melting point and high resistance. Copper has high melting point, not suitable for fuse. Silver expensive. Aluminium not typical.
Explanation:
Position-time graph as parabola: x = x₀ + ut + ½at². This quadratic form indicates constant acceleration 'a'. If acceleration were changing, the graph would be cubic or higher order. Constant velocity would produce a straight line (linear graph). Upward opening parabola implies positive acceleration. Graph interpretation skill is essential: slope of x-t graph = velocity; curvature indicates acceleration. Memory tip: Parabolic x-t graph ⇔ constant acceleration; linear x-t graph ⇔ constant velocity. Competitive exams frequently test graph-concept correlations.
No comments yet. Be the first to start the discussion!