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A block of mass 10 Kg accelerates from rest to a velocity of 20 m/s in 5s under the influence of an external force. What is the work done by the external force?(a) 2000 J(b) -2000 J(c) 20000 J(d) -20000 JI have been asked this question by my school principal while I was bunking the class.Question is taken from Work topic in chapter Work, Energy and Power of Physics – Class 11

Answer»

The correct answer is (a) 2000 J

To elaborate: The acceleration can be FOUND out by using the INITIAL and FINAL velocities and the time taken. Acceleration = 4 m/s^2. Force can be found out by the second law. By the second EQUATION of motion the distance covered in 5 s can be found which is equal to 50 m. Work can be found out by MULTIPLYING the force and the distance covered. Work = 2000 J.



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