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1) A ball is released from the top of a tower. The ratio of work done by force of gravity in first, second and third second of motion of the ball is {answer should come 1:3:5}

2) The kinetic energy of a body of mass 2 kg and momentum of 2 Ns is:
{answer should come 1 joule}
 
3)A block of mass m is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration a. The work done by tension on the block during t second is (u = 0) :      {diagram is given}      
{answer should come [tex] \frac{m}{2}(g+a) a t^{2} [/tex]}

1 A ball is released from the top of a tower The ratio of work done by force of gravity in first second and third second of motion of the ball is answer should class=

Answer :

kvnmurty
gravity Force = m g
distance traveled in t seconds = s = u t + 1/2 g t² = 1/2 g t²
total distance traveled at t = 1, t= 2, t  =3 sec. are g/2, 2 g, 9g/2
distance traveled in 1st, 2nd and 3rd second are = g/2, (2g-g/2), (9g/2-2g)
       = g/2 , 3g/2,  5g/2
work done during 1st, 2nd, 3rd seconds are = m g²/2,  mg²*3/2 , mg² 5/2
ratio = 1 : 3 : 5
==================
  KE = p²/2m = 2²/2*2 = 1 J
=================
 
    T - m g =  m a
     T = m (g+a)
work done by Tension = W = T * displacement = T * [1/2 a t² ]
   W1  = m (g+a) a t² / 2

just for clarity,  Work done by gravity = W2 = - m g [1/2 a t² ]
 
Net work done on block and actual change in its energy = W1 + W2 = m a² t² /2

Answer:

1:3:5

Explanation:

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