General Science Force and Motion

Exercise: 9.2

Q1. What are machines?
Ans: Machines are devices which are used to reduce the human effort and make the work easier.

Q2. Name three objects that you exert force on, while doing school work.
Ans: Pencil, Eraser, Sharpener.

Q3. Name these.
Ans:
1. Straight slanted surface: Inclined plane.         2. A rod that pivots at a fixed point pulley.
3. An inclined plane wrapped in spiral screw. 4. Double inclined plane Wedge.
5. Machine consisting of a grooved wheel that holds a rope wheel and axle.

Q4. Complete the following concept map.

Exercise : 9.4 Explain how atmospheric helps you drink throw a straw?
Ans: When we take a sip through straw, we are actually putting air out of straw, the greater air pressure outside the straw pushes the liquid into the straw, so it rises up into mouth.

Additional Q/A

Q1. What is a lever? How does it work?
Lever:
A lever is a rigid rod or bar straight or curved which moves on a fixed point. The fixed point is called the fulcrum, or the pivot. A push or a pull is the force put on the one end of the lever arm. This is called the effort. This force is trying to overcome the weight of the object. This weight is called the load. In many tools and machines, levers work together in pairs and the fulcrum is often at the point where the levers are fixed together.

Q2. How many kinds of lever are there? Explain them with the help of diagram.
Ans: There are three kinds of lever. We use in our daily life. Each kind depends on the relative positions of the effort, load and fulcrum.

First kind of lever:
The first kind of lever has its fulcrum between the load and effort Example: crow bar, claw hammer, and a pair of scissors are the examples of first kind of lever.

Second kind of lever:
The second kind of lever has its load between the fulcrum and the effort.
Example: wheel barrow, bottle opener and door are the examples of second kind lever.

Third kind of lever:
In the third kind of lever, the effort lies between the load and the fulcrum. Example: Human arm, broom, tweezer, and knife are the examples of third kind of lever.

Q3. Define pulley.
Ans: Pulley:
The pulley helps us to lift heavy things straight up. A pulley is a kind of wheel with groove over which we can put a rope. The groove prevents the rope from slipping out. Craines use pulley system to lift heavy loads.

Q4. Write uses of atmospheric pressure in our daily life.
Ans: 1. Motor car tyres, bicycles tyre and tyres of other wheeled vehicles are kept hard due to air                pressure.
2. The straw used for drinking also work because of air pressure.
3. When dropper is placed in a solution then solution rises up due to air pressure.
4. A syringe also works by air pressure.

Q5. What is a screw?
Ans: A screw is an inclined plane that is wrapped in a spiral. The spiral shape groove is called a thread. A spiral stair case is like a giant screw.

Q6. Define inclined plane.
Ans: Inclined plane or ramp is another kind of simple machine. A ramp is a slope with one end higher than the other. It is used for moving heavy objects up and down.

Fill in the blanks:

1. There are six types of simple machine.
2. The simplest kind of machine is the lever.
3. A wedge has double inclined plane that moves.
4. A wheel on the end of an  axle make a simple machine.
5. The spiral shaped groove is called a thread.
6. A syringe works by air pressure.

Posted in: Class-6th,S.Q.A