Energy

Q. A wind - powered generator converts wind energy into electrical energy. Assume that the generator converts a fixed fraction of the wind energy intercepted by its blades into electrical energy. For wind speed V, the electrical power output will be proportional to

1. $V^3$
2. $V^4$
3. $V$
4. $V^2$

Q.

The Diesel Generator you saw usually in Family functions or industries converts ___.

1. chemical to mechanical

2. mechanical to electrical Energy

3. potential to kinetic energy

4. electrical to mechanical Energy

Q. Two unequal masses are tied together with a cord with a compressed spring in between.
Which one is correct ?

1. None of above answer is correct
2. Both mases will have equal KE.
3. Lighter block will have greater KE.
4. Heavier block will have greater KE.

Q.

A spinning wheel A is brought in contact with another wheel B which is initially at rest. Because of the friction at contact, the second wheel also starts spinning, then which of the following energies of B won't change?

1. Mechanical

2. Kinetic

3. Internal

4. Potential

Q. Capacity to do work is called energy.

1. False
2. True

Q. An object of mass $50\text{kg}$ is raised to a height of $10\text{m}$ above the ground. If the object is allowed to free fall. What is kinetic energy, when it is half way down? ($g=10{\text{m/s}}^2$)

1. $1250\text{J}$
2. $2500\text{J}$
3. $3750\text{J}$
4. $5000\text{J}$

Q. An ideal massless spring $S$ can be compressed by $1m$ by a force of $100N$ in equilibrium. The same spring is placed at the bottom of a frictionless inclined plane at ${30}^{\circ }$ to the horizontal. A $10kg$ block $M$ is released from rest at the top of the incline and is brought to rest momentarily after compressing the spring by $2m$. If $g=10m/s^2$, what is the speed of mass just before it touches the spring?

1. $\sqrt{20}m/s$
2. $\sqrt{30}m/s$
3. $\sqrt{10}m/s$
4. $\sqrt{40}m/s$

Q.

The blades of a windmill sweep out a circle of area A. (a) If the wind flows at a velocity v perpendicular to the circle, what is the mass of the air passing through it in time t?(b) What is the kinetic energy of the air? (c) Assume that the windmill converts 25% of the wind’s energy into electrical energy, and that $A=30m^2$, v = 36 km/h and the density of air is $1.2kg{m}^{-3}$. What is the electrical power produced?

Q. Under the action of a force, a $2\text{kg}$ body moves such that its position $x$ as a function of time t is given by $x=\frac{t^3}{3}$, where $x$ is in meter and $t$ in second. The work done by the force in the first two seconds is

1. $1600\text{J}$
2. $1.6\text{J}$
3. $160\text{J}$
4. $16\text{J}$

Q.

Which of the following statements are correct regarding energy?

1. It is capacity to do work

2. It cannot be created nor be destroyed

3. It can be transferred from one object to other

4. All of these