Explanation
It is given that 2 kg and 3 kg blocks are placed on a smooth horizontal surface and connected by spring which is unstretched initially. Let v is the final velocity then from conservation of momentum:
5v=2(−4v0)+3(v0)
5v=−8v0+3v0
v=−v0...........(1)
Let x is the maximum elongation in the spring. From conservation of energy:
12(2)(−4v0)2+123(v0)2=12kx2+125(v0)2(fromequation(1))
16v02+32v20=12kx2+52v20
15v20=12kx2
The energy stored in spring is 15v20
Given:
The mass of the bucket m=20 kg
The height of the building h=20 m
Work done by the worker=Potential energy of bucket at the top of the building
∴W=mgh
⇒W=20×9.8×20
⇒W=3920J
Thus, the required work done is 3.92kJ
K.E1 = K.E2
12 M1 v21 = 12 M2 v22
Two identical balls are released from positions as shown. They collide elastically on horizontal surface. Ratio of heights attained by A & B after collision is( All surface are smooth,neglect energy loss at M & N)
Work done in stretching wire
=12YAL2L=12F.l
Where
L= length of wire
l= increase in length
We know that
E=12×F×AL
=12×200×10−3
=0.1J
Hence (A) option is correct.
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