Work Energy and Power-Quiz-7

WORK ENERGY AND POWER Quiz-7

Dear Readers,

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.

One end of an unstretched vertical spring is attached to the ceiling and an object attached to the other end is slowly lowered to its equilibrium position. If S is the gain in spring energy and G is the loss in gravitational potential energy in the process, then

•  S=G
•  S=2G
•  G=2S
•  None of these

Solution

Q2.

•  0.25
•  0.35
•  0.45
•  0.55

Solution

Q3.  

Statement I In an elastic collision between two bodies, the relative speed of the bodies after collision is equal to the relative speed before the collision. 

Statement II In an elastic collision, the linear momentum of the system is conserved.

•  Statement I is true ,statement II is true; statement II is a correct explanation for statement I
•  Statement I is true, Statement II is true; statement II is not correct explanation for statement I
•  Statement I is true, Statement II is false
•  Statement I is false, Statement II is True

Solution

In case of elastic collision ,coefficient of restitution e=1 or Relative speed of approach =relative speed of separation.

Q4. A stone of mass 1 kg tied to a light inextensible string of length L=10/3 is whirling in a circular path of radius L in a vertical plane. If the ratio of the maximum tension in the string to the minimum tension is 4 and if g is taken to be 10 ms^(-2), the speed of the stone at the highest point of the circle is

•  10 ms^(-1)
•  5√3 ms^(-1)
•  10√3 ms^(-1)
•  20 ms^(-1)

Solution

Q5.

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Solution
 

Q6. 

A bus can be stopped by applying a retarding force F when it is moving with speed v on a level road. The distance converted by it before coming to rest is s. If the load of the bus increases by 50% because of passengers, for the same speed and same retarding force, the distance converted by the bus to come to rest shall be

•  1.5s
•  2s
• 1s
•  2.5s

Solution

Q7.

A particle of mass m is projected at an angle α to the horizontal with an initial velocityu. The work done by gravity during the time it reaches its highest point is

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Solution

Q8.

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Solution

Loss in PE = Work done against friction
⇒mgh=μ mg s ⇒ μ=h/s

Q9. The potential energy of a particle is determined by the expressionU=α(x^2+y^2), where α is a positive constant. The particle begins to move from a point with coordinates (3, 3), only under the action of potential field force. Then its kinetic energy T at the instant when the particle is at a point with the coordinates (1, 1) is

•  8α
•  24α
•  16α
•  Zero

Solution

Q10. 

In which of the following cases can the work done increase the potential energy?

•  Both conservation and non-conservation forces
•  Conservation force only
•  Non-conservation force only
• Neither conservation nor non-conservation forces

Solution
In case of non-conservation forces, the work done is dissipated as heat, sound, etc i.e., it does not increase the potential energy. But in case of conservative forces, work done is responsible for increasing or decreasing the potential energy