Explanation
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
∴
\Rightarrow W = 20 \times 9.8 \times 20
\Rightarrow W = 3920\;{\rm{J}}
Thus, the required work done is 3.92\;k{\rm{J}}
K.E_1 = K.E_2
\dfrac{1}{2} M_1 v_1^2 = \dfrac{1}{2} M_2 v_2^2
Given that,
Spring constant k=100
Mass m=10\,kg
Stretching x=2\,m
We know that,
The work done is
W=\dfrac{1}{2}k{{x}^{2}}
W=\dfrac{1}{2}\times 100\times 4
W=200\,J
Hence, the work done is 200\ J
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
=\dfrac {1}{2}\dfrac {YAL^{2}}{L}=\dfrac {1}{2}F.l
Where
L= length of wire
l= increase in length
We know that
E=\dfrac {1}{2}\times F \times AL
=\dfrac {1}{2}\times 200 \times 10^{-3}
=0.1J
Hence (A) option is correct.
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