Efficiency of Machines

Q.

A machine is, not 100% efficient because :

1. the output of the machine is always less than the input.

2. the output of the machine is always more than the input.

3. the output of the machine is always equal to the input.

4. None of these.

Q.

When a body falls from an aeroplane its velocity increases. Which energy of the body will increase?

1. Kinetic energy

2. Potential energy

3. Acceleration

4. Rest mass

Q.

A uniform plank of a see-saw is 5m long and supported at its center. A boy weighing 40kgf sits at a distance of 1.5m from one end of the see-saw whereas must a girl weighing 25kgf sit on the other end of the see-saw so as to balance the boy.

Q.

A machine displaces a load of 125kgf through a distance of 0.30m, while an effort of 12.5kgf acts through a distance of 4.0m. calculate the mechanical advantage.

Q.

What kind of energy is possessed by a fish that is moving in water?

Q.

Why is a machine not 100% efficient?

1. Different parts of the machine are not smooth and rigid

2. String in it (if any) is not perfectly elastic

3. Moving parts are not weightless

4. All of the above

Q.

If the Velocity Ratio(V.R) of a simple machine is more than that of a Mechanical Advantage(M.A), then which one of the following choices is the best suit?

1. Efficiency remains same.

2. Efficiency becomes zero.

3. Efficiency reduces.

4. Efficiency becomes greater than 80%.

Q. The momentum of an object is the product of its mass and _____.

1. weight
2. volume
3. speed
4. velocity

Q.

The efficiency of a machine is the ratio between ___

1. $\frac{Velocityratio}{Mechanicaladvantage}$

2. $\frac{Mechanicaladvantage}{Velocity}$

3. $\frac{Mechanicaladvantage}{load}$

4. $\frac{Mechanicaladvantage}{Velocityratio}$

Q.

A machine is operated by an effort of 25 N and the effort has a downward displacement of 2.5 m in raising a load of weight 100 N through 10 cm. What is the efficiency of machine (in %) ?

1. 250

2. 40

3. 25

4. 16

Q. If there is no net force acting on an object, the total momentum of the object with time will:

1. Become zero
2. Decrease
3. Increase
4. Remain same

Q.

The input power to a machine is 1500 W. And its efficiency is 80%. Then the output power by the machine is :

1. 1100 W

2. 1200 W

3. 800 W

4. 1500 W