Work Energy and Power Test

Result

Work Energy and Power Test - 55

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Weekly Quiz Competition

Question 1
1 / -0

does not vary from point to point in space Which pair of the following forces will never give resultant force of 2 N?

A
1 N and 3 N

B
2 N and 2 N

C
1 N and 1 N

D
1 N and 4 N

Solution

$$1N$$ and $$4N$$ will never give $$2N $$
mind it$$,$$ if the side lengths of a triangle is $$a,b,c$$
$$a+b>=c$$
$$b+c>=a$$
$$c+a>=b$$
Hence,
option $$(D)$$ is correct answer.
Question 2
1 / -0

The speed of a motor increases from 1200 rpm to 1800 rpm in 20 s. How many revolutions does it make during these second?

A
400

B
600

C
500

D
700

Solution
Question 3
1 / -0

A hollow smooth uniform sphere $$A$$ of mass $$m$$ rolls without sliding on a smooth horizontal surface. It collides elastically and head-on with another stationary smooth hollow sphere $$B$$ of the same mass mm and same radius. The ratio of the kinetic energy of $$B$$ to that of $$A$$ just after the collision is

A
$$1 : 1$$

B
$$2 : 3$$

C
$$3 : 2$$

D
$$\rm{None}$$

Solution

The sphere is rolling on a smooth surface i.e., no energy is lost to friction and the kinetic energy of sphere A is transferred to the sphere B without any loss as the collision is head-on and elastic.
Thus, the kinetic energy of sphere A and sphere B are equal their ratio will be 1:1
Question 4
1 / -0

AB is long frictionless horizontal surface. One end of an ideal spring of spring constant K is attached to a block of mass m, which is being moved left moved left with constant velocity v, and another end is free.Another block of mass 2m is given a velocity 3v towards the spring. Work done by an external agent in moving m with constant velocity v in a long time will be:

A
$$ - 5m{v^2}$$

B
$$ - 8m{v^2}$$

C
$$ - 3m{v^2}$$

D
None of these

Solution
Question 5
1 / -0

The work done by a force $$F=(-6x^3\hat
i)$$ in displacing a particle from $$x = 4m$$ to $$x = -2m$$ is:

A
$$- 240$$ J

B
$$360$$ J

C
$$420$$J

D
will depend upon the path

Solution
Question 6
1 / -0

The tension in the string revolving in a vertical circle with a mass m at the end which is at the lowest position

A
$$\dfrac{mv^2}{r}$$

B
$$\dfrac{mv^2}{r}-mg$$

C
$$\dfrac{mv^2}{r}+mg$$

D
$$mg$$

Solution

R.E.F image
$$F_{c}$$ Fore of centrifygal
$$T=F_{c}+mg$$
$$=\frac{mv^{2}}{12}+mg$$
so, option (c)
Question 7
1 / -0

When a simple pendulum is rotated in a vertical plane with constant angular velocity, centripetal force is:

A
maximum at highest point

B
maximum at lowest point

C
same at all points

D
zero

Solution
Question 8
1 / -0

Work done by air when it expands from 50 litres to 150 litres at a constant pressure of 2 atmospheres is:

A
$$2\times { 10 }^{ 4 }J$$

B
$$2\times { 10 }0J$$

C
$$2\times { 10 }^{ 5 }\times 100J$$

D
$$2\times { 10 }.5\times 100J$$

Solution
Question 9
1 / -0

A block of mass 10 kg is moving up on an inclined plane with constant acceleration 2 m/sec by applying a constant force F as shown in the fig. The work done on the block by applied force F in 2 s is

A
480

B
240

C
960

D
none

Solution
Question 10
1 / -0

A force $$\vec { F } =\left( { 3x }^{ 2 }+2x-7 \right) $$ N acts on a 2 kg body as a result of which the body gest displaced x=0 to x=5 cm. The work done by the force will be-

A
35 Joule

B
70 Joule

C
115 Joule

D
270 Joule

Solution