A two-car train, with data as given in Fig. is pulled by a child on a horizontal frictionless surface. The strings are massless. The force exerted by car A on the string S is:

Correct answer: D. 15N

  • A. 10N
  • B. 20N
  • C. Zero
  • D. 15N

Explanation

To solve this problem, use Newton's second law, F = ma. First, find the total mass of the two-car system. Then, determine the acceleration by dividing the total force applied by the total mass. Since the surface is frictionless, the force exerted by car A on the string S is equal to the mass of car A multiplied by the common acceleration. The correct force is 15N. Other options are incorrect because they either do not consider the entire system or miscalculate the acceleration.

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