Screw

Q.

(a) What is a screw?

(b) Give three uses of a screw.

Q. What is a screw? Give two examples.

Q.

Which of the following is non-conservative force?

1. Electrostatics force

2. Gravitational force

3. Viscous force

4. Spring force

Q.

A stone of mass $500g$ is thrown vertically upwards with a velocity of $15m{s}^{-1}$. Calculate

(i) The $PE$ at the greatest height.

(ii) $KE$ on reaching the ground.

(iii) The total energy at its half-way point.

Q.

Explain any two examples when work done is

(i) positive.

Q.

Calculate the horsepower of the motor of an elevator, which can carry $10$ persons of the average mass of $60kg$ through a vertical height of $20m$ in $30s$. [Take g =$10N/kg$, $1HP=750W$]

Q.

A pulley system has 5 pulleys in all, its velocity ratio is

1. 5

2. less than 5

3. more than 5

4. none of these

Q.

What are the conditions of doing work?

Q.

A lead pallet of mass 10g leaves an air gun with a velocity of 40 ms^-1.what is the magnitude of potential energy stored by its spring?

Q.

State whether the work done by an applied force on a body moving on through a horizontal plane with uniform velocity is positive or negative.

Q.

Screw is a modified form of a lever.

1. True

2. False

Q.

The doorknob is an example of the wheel and axle.

1. True
2. False

Q.

What is an ideal machine? Is it possible practically?Explain.

Q.

Find the power of an engine required to lift ${10}^5$$kg$ of coal per hour from a mine of $360m$ deep.

Q.

Two bodies A and B of masses 4 kg and 16 kg respectively have the same kinetic energy. The ratio of the velocity of A and B is

1. 1:2

2. 2:1

3. 2:3

4. 3:2

Q. Which simple machine keeps the bottle cap tight?

1. Screw
2. Wedge
3. Pulley
4. Lever

Q. State three differences between three classes of levers.

Q. _______ is an inclined plane wrapped in a spiral around a rod.

1. Pulley
2. Rubber
3. Screw
4. Wedge

Q.

Mention the name of three form of kinetic energy and give one example of each form.

Q.

______ can be thought of as an inclined plane wrapped around a cylinder.

1. Crowbar

2. Wheel and axle

3. Screw

4. Pulley

Q.

A pulley system with a velocity ratio of 4 is used to lift a load of 100kgf through a vertical height is 15m. The effort required to do so is 40kgf which is applied in the downward direction. calculate Workdone by the effort

Q.

A pair of scissors is used to cut a piece of a cloth by keeping it at a distance of 8.0 cm from its rivet and applying an effort of 10 kgf by fingers at a distance of 2.0 cm from the rivet.

(a) Find : (i) the mechanical advantage of scissors, and (ii) the load offered by the cloth.

(b) How does the pair of scissors act : as a force multiplier or as a speed multiplier ?

Q.

Name some simple machines.

Q. In a lever, fulcrum is at one end at a distance of $30cm$ from the load and effort is at the other end at a distance of $90cm$ from the load. Find the mechanical advantage of the lever.

Q.

A crowbar of length 2.0 m is used as a machine to lift a box of 100 kg f by placing a fulcrum at a distance of 0.1 m from the box. Calculate the effort required.

Q.

Potential energy of a body depends on its mass, velocity and height above the ground.

1. True
2. False

Q.

Choose among the following which is/are complex machines ?

1. Bicycle

2. Screw

3. Lawn Mower

4. Can opener

Q.

The point at which a lever is supported is called an axle.

1. True
2. False

Q.

What is the amount of work done by a man pressing a rigid wall with a force of 200 N?

Q.

In which case work is done and why?

A porter carrying a load on his head walking along a level road.