Law of Conservation of Energy

Q.

A ball of mass 200g falls from a height of 5m. What is its kinetic energy when it just reaches the ground. (Take $g=9.8m{s}^{-2}$ )

Q.

Question: If air resistance is zero, the sum of potential and kinetic energy of a freely falling body will

Q. State and explain the law of conservation of mechanical energy with an example. [3 Marks]

Q.

If air resistance is zero, the sum of potential and kinetic energy of a freely falling body will:

1. zero
2. increase
3. decrease
4. remain constant

Q. If a body is raised to a height then it gains potential energy so if the body goes at a very big height and gains a high pe then when escapes into space where there is no gravity where does the pe goes




I got the answer in byjus before also but can you give the answer with a example

Q.

When an apple falls freely from the tree towards the ground, then its total mechanical energy throughout the fall will:

1. decreases

2. first increases and then decreases

3. remains constant

4. increases

Q.

What is kinetic energy and potential energy??

Q.

A runner possesses only kinetic energy. What kind of energy is possessed by a flying bird?

1. Potential energy only
2. Kinetic energy
3. Can't say
4. Both kinetic and potential energy

Q.

A ball is thrown from the top of a building. As it approaches the ground which of the following energy decreases?

1. Kinetic energy

2. Potential energy

3. Mechanical energy

4. Both kinetic and potential energy

Q.

The law of conservation of energy states that:

1. The supply of energy is limited and must be conserved.

2. Energy must be conserved and it shouldn’t be wasted.

3. The total amount of energy is constant.

4. Energy cannot be used faster than it is created.

Q. A lift is designed to lift a load of $1000\text{kg}$, through $6$ floors of a building with an averge height of $3.5\text{m}$ per floor in $6\text{s}$. The power of the elevator, neglecting energy losses, will be: $\left[1\text{mark}\right]$

A. $3.5\times {10}^4\text{W}$
B. $4.3\times {10}^4\text{W}$
C. $2.2\times {10}^4\text{W}$
D. $5.6\times {10}^4\text{W}$

Q. Consider a car moving on a straight road with a speed of 100 m/s . The dis†an ce at which car can be stopped is \{coefficient of kinetic friction is 0.5\}

Q.

As we all know the earth's gravitational force attract all the objects towards it at the speed of 9.8m/s. But if we fall from a great height, let consider that we jump from an aeroplane. As we jump our speed is low but as we get closer to the earth's surface our speed starts increasing. Why this happen?

Q. Does the work done is moving a body depend on how fast or how slow the body is moved?

Q. A stationary ball of mass $m$ and potential energy $U$ is dropped from a height. If the total mechanical energy is constant throughout the fall, then the velocity with which it reaches the ground is:

1. $\sqrt{\frac{U}{m}}$
2. $\sqrt{\frac{U}{2m}}$
3. $\sqrt{\frac{2U}{m}}$
4. $\sqrt{\frac{U}{m}}$

Q. Answer the question:
A cyclist travels down a hill from rest at point X, without pedalling.
The cyclist applies his brakes and thw cycle stops at point Y.
Which energy changes have taken place between X and Y ?

1. gravitational potential $\to$ kinetic $\to$ thermal (heat)
2. gravitational potential $\to$ thermal (heat) $\to$ kinetic
3. kinetic $\to$ gravitational potential $\to$ thermal (heat)
4. kinetic $\to$ thermal (heat) $\to$ gravitational potential

Q. A free-fall object eventually stops on reaching the ground. What happens to its kinetic energy?

Q.

A body is falling from a height h. At a height h/2, it will possess ____ energy.

1. Only potential energy
2. More potential less kinetic
3. Half potential half kinetic
4. Only kinetic energy

Q. Give one example of a body that has potential energy, in each of the following :
(a) due to its position at a height;
(b) due to its elongated stretched state.

Q.

The potential energy of a body of mass 3 kg on the surface of a planet is 54 joule. The escape velocity will be

1. 18 m/s
2. 162 m/s
3. 36 m/s
4. 6 m/s

Q. In which of the following cases, the speed of the ball will be more?

1. In both cases speed will be same
2. $B>A$
3. $A>B$
4. None of the above

Q. Assertion :A ball is dropped from a certain height above the free surface of ideal fluid. When the ball enters the liquid it may accelerate or retard. Reason: Ball accelerates or retards, it all depends on the density of ball and the density of liquid.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect