## WORK ENERGY AND POWER Quiz-11

Work power energy is the most important chapter when it comes to mechanics, for JEE (Advanced). The chapter is quite tricky and takes a lot of time and devotion on your part to understand and master. But this chapter is a complete gold medal for almost all the questions of the mechanics can be solved by the work power energy approach if you master this topic..

Q1.
•  On both the routes is same
•  On route I is more
•  On route II is more
•  On both the routes is zero
Solution
Work done, W=mgh+Î¼ghL Which is a constant

Q2.
A particle is projected vertically upwards with a speed of 16 ms^(-1). After some time, when it again passes through the point of projection, its speed is found to be 8 ms^(-1). It is known that the work done by air resistance is same during upward and downward motion. Then the maximum height attained by the particle is (take g=10 ms^(-2))
•  8 m
•  4.8 m
•  17.6 m
•  12.8 m
Solution

Q3.
Which of the following graphs depicts the variation of kinetic energy of a ball bouncing on a horizontal floor with height? (Neglect air resistance)
•
•
•
•
Solution
If h be the height of the ball above the floor and H the height from which the ball is dropped, then E=1/2 mv^2=loss in PE or KE=mg(H-h) or KE=-mgh+mgH, which is of the form y=-ma+c

Q4.
A machine delivers power to a body which is proportional to velocity of the body. If the body starts with a velocity which is almost negligible, then the distance covered by the body is proportional to
•  √V
•  ∛(V/2)
•  v^(5/3)
•  v^2
Solution

Q5.
•  14.14 m/s
•  7.07 m/s
•  5 m/s
•  25 m/s
Solution

Applying the work-energy theorem, we get 1/2 mv^2-0=F×R+mg×R
1/2×1/2×v^2=5×5+1/2×10×5=50
v=√200=14.14 ms^(-1)

Q6.
•  10 cm
•   5 cm
• 12 cm
•  8 cm
Solution
1/2 kx^2=mgh ⇒ x=√(2mgh/k)

Q7.
•  1/4
•  3/4
•  1/2
•  1/8
Solution

Q8.
•  b/2a
•  √(2a/b)
•  √(2b/a)
•  a/2a
Solution

Q9.
•  x1 is in stable equilibrium
•  x2 is in stable equilibrium
•  x3 is in stable equilibrium
•  None of these
Solution
x=x1 and x=x3 are not equilibrium positions because du/dx≠0 at these points x=x2 is unstable equilibrium position, as U is maximum at this point

Q10.

•
•
•
Solution

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