Work Energy and Power-Quiz-4

WORK ENERGY AND POWER Quiz-4

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.

A projectile is fired with some velocity making certain angle with the horizontal. Which of the following graphs is the best representation for the kinetic energy of a projectile (K.E.) versus its horizontal displacement(x)?

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Solution

Q2.

Two masses of 1g and 4g are moving with equal kinetic energies. The ratio of the magnitudes of their linear momenta is

•  4∶1
•  √2 ∶1
•  1∶2
•  1∶16

Solution

Q3.  A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time t is proportional to

•  √t
•  t^(3/4)
•  t^(3/2)
•  t^2

Solution

Q4. 

•  At point away from the origin, the particle is in unstable equilibrium
•  For any finite non-zero value of x, there is a force directed away from the origin
•  If its total mechanical energy is k/2, it has its minimum kinetic energy at the origin
•  For small displacements from x=0, the motion is simple harmonic

Solution

Q5.The displacement x in metre of a particle of mass m kg moving in one dimension under the action of a force is related to the time t in second by the equationx=(t-3)^2. The work done by the force (in joules) in first six seconds is

•  18m
•  Zero
•  9m/2
•  36m

Solution
 

Q6. 

The distance converted by a body to come to rest when it is moving with a speed of 4 ms^(-1) is s when a retarding force F is applied. If the KE is doubled, the distance covered by it to come to rest for the same retarding force F is

•  4 s
•  6 s
• 2 s
•  8 s

Solution
From the above question, s∝KEi If KE is doubles, s is also doubled

Q7.

An engine pumps water continuously through a hole. Speed with which water passes through the hole nozzle isv, and k is the mass per unit length of the water jet as it leaves the nozzle. Find the rate at which kinetic energy is being imparted to the water

•  1/2 kv^2
•  1/2 kv^3
•  V^2/2k
•  V^3/2k

Solution

Q8.

•  6 Joule
•  T5 Joule
•  8 Joule
•  2 Joule

Solution

Q9.

Two men A andB, each weighing 80 kg, run up the same stair case. While A does it in 20 s. B does it in 15 s. The ratio of the powers developed by A and B is

•  4/3
•  3/4
•  1/2
•  1/4

Solution

PA/PB =tB/tA =15/20=3/4

Q10. 

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Solution