The kinetic energy of a body becomes four times its initial value. The new momentum will be:
A. Four times the initial
B. Twice the initial
C. Half the initial
D. Same as initial
Answer: Option B
Solution (By JKSSB Mock Tests)
Kinetic energy KE = p²/(2m), where p is momentum. Thus p = √(2m·KE). If KE becomes 4 times, p_new = √(2m·4KE) = 2√(2m·KE) = 2p_initial. Hence momentum doubles. This relationship shows momentum scales with square root of kinetic energy for constant mass. Memory tip: p ∝ √KE when mass constant. This conceptual link between momentum and kinetic energy is frequently tested in competitive exams to assess depth of understanding beyond rote formula memorization. Always derive relationships when direct formulas aren't recalled.
A block of mass 10 kg is accelerating at 2 m/s^2 on a horizontal surface under an applied force of 50 N. What is the magnitude of the frictional force opposing its motion?
Explanation:
According to Newton's Second Law, the net force on the block is F_net = mass * acceleration = 10 kg * 2 m/s^2 = 20 N. The net force is the difference between the applied forward force and the opposing frictional force (F_net = F_applied - F_friction). So, 20 N = 50 N - F_friction. Solving for friction gives F_friction = 50 - 20 = 30 N.
Explanation:
Leading zeros not significant. '450' has three digits, but the trailing zero after decimal is significant (4,5,0). So 3 significant figures. 0.00450 is 3 SF.
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