SOLUTION

The science of studying sound and sound waves is called acoustics.

SOLUTION

Our earlobe acts like a funnel which collects various sounds and sends them to our ears.

SOLUTION

Light and sound are forms of energy.

SOLUTION

It produces vibrations which are transferred to the listener through air.

SOLUTION

Music is an example of pleasing sound. It relaxes us and makes us feel happy. Therefore everyone enjoys musical sound.

SOLUTION

Those sounds which are unpleasant and which are produced at a higher level are called loud sounds. These sounds irritate us and can cause problems like headache.

SOLUTION

The speed of sound depends on the medium through which it passes. If sound passes through solid medium, it will travel fast whereas if it passes through air it will travel slowly.

SOLUTION

Vibrations are carried forward by a medium like air, water or some solid object.

SOLUTION

Vibrations are the sensations produced by a moving object.

SOLUTION

a.waves

b.vibration

c.  ears

d.solid

e.noise

SOLUTION

Thunder, chirping of birds, rustling of leaves, falling water etc.

SOLUTION

SOLUTION

Sound of alarm clock, sound of vehicle horns, sound of school bell etc.

SOLUTION

Atomic energy

SOLUTION

When the atoms join or break, large amount of energy is released. This enormous amount of energy released is known as Atomic energy.

SOLUTION

Water stored at a height possesses huge amount of energy, which can be utilised when it is allowed to fall from that height.

In hydropower plant, this water falls on a turbine which is in connected to generator. Hence electricity is generated.

SOLUTION

The energy obtained from sun is called solar energy. The Sun is the main source of energy on earth. Green plants need solar energy to prepare their food.

SOLUTION

They are:

Light energy

Sound Energy

Heat Energy

Magnetic energy

Electrical energy

SOLUTION

All living things require energy for their growth and development. They need energy to do everything. Energy is the ability to do work.

SOLUTION

For pushing apart solid objects, the sharp end of the wedge is placed on it. It is then hammered from the wider end. As the sharp end penetrates the object, it tears apart the object in a lateral direction.

SOLUTION

Pulley

SOLUTION

Our ancestors used wedge shaped instruments to tear the flesh of the animals and to cut things apart.

SOLUTION

1. With the help of the pencil, draw an 'L' on the paper, having a height of 16 cms and a base of 8cms.

2. Now, to make a right triangle, join the two open ends of the L.

3. Cut the triangle. Wrap the triangle around the pencil and secure it with the piece of a tape.

SOLUTION

a. Disagree

b. Agree

c. Disagree

d. Agree

e. Agree

SOLUTION

a. pulley

b. wedge

c. screw

d. lever

SOLUTION

SOLUTION

a. raise, move

b. Energy

c. solar energy

d. will mills

e. lever

SOLUTION

Door knob and Car wheel

SOLUTION

See-saw    Fishing-rod    Can opener    Door Knob

SOLUTION

Lever

SOLUTION

Wheel and axle

SOLUTION

a. A sloping surface which connects a lower level to higher level is known as inclined plane.

b. An inclined plane wrapped around a pole is called screw.

SOLUTION

1. Pulley: Drawing of water from well

2. Wedge: Cutting of wood

SOLUTION

Loam is best for growing plants because it contains humus which is fertile and help the plant to grow.

SOLUTION

Loamy soil is a mixture of sand and can hold air and water. It contains humus and is best for growing plants.

SOLUTION

1. It is used for making statues, parks and fountains.

2. It is used for surfacing of roads.

SOLUTION

1. GRANITE
2. MARBLE
3. SLATE
4. PUMICE

SOLUTION

a. It is used for construction of buildings

b. It is used for making blackboards

SOLUTION

SOLUTION

Terrace farming reduces the force of flowing water on the soil and thus helps in reducing soil erosion.

SOLUTION

The removal of fertile top soil by the action of water and wind is known as soil erosion.

SOLUTION

Cutting down trees in large number, construction of roads and buildings and overgrazing are activities which are responsible for increasing soil erosion.

SOLUTION

When sun, wind and water acts upon the top layer of soil, it gets washed away, which is rich in humus and hence soil loses its fertility. Thus, soil erosion occurs.

SOLUTION

Rocks are heated up and cooled down by falling rain. This constant heating and cooling of rocks causes cracks in the rocks which become larger with time. They break into small pieces because of the action of wind, water and temperature. Rubbing of the smaller pieces will lead to more breakage and hence soil is formed.

SOLUTION

1. Agree
2. Agree
3. Disagree
4. Agree
5. Disagree

SOLUTION

SOLUTION

a. rocks

b. humus

c. Loamy

d. Sandy

SOLUTION

1. A mixture of rock particles which are coarser than sand is known as gravel.
2. The breaking down of rocks and minerals is known as weathering.

SOLUTION

Few years back, the amount of soil removed due to soil erosion was equal to the amount of soil formed naturally. Hence, soil erosion was a natural process, but nowadays it has been disturbed by human activities.

SOLUTION

1. Wind, water and temperature act on rocks.
2. Rocks break down into smaller pieces.
3. These smaller pieces turn into sand.
4. Sand mix with decaying plants and animals.
5. The soil is formed.

SOLUTION

SOLUTION

Inclined plane

SOLUTION

Heat energy

SOLUTION

1. They make our work easier and faster.

2. They change the direction of the applied force.

3. They help us to do work by applying less force.

SOLUTION

Vise and Bolt

SOLUTION

Lever

SOLUTION

A wedge is an object having at least one slanting side which ends in a sharp edge.

SOLUTION

Moving air is called wind.

SOLUTION

In the second case, we used a support under the heavy stone because of which we can easily lift it.

SOLUTION

SOLUTION

All machines or vehicles have rubber grip on their handles because rubber grip creates more friction and lets a person to grasp the handle efficiently.

SOLUTION

We feel warm on rubbing our palms even in winters because friction creates heat energy.

SOLUTION

Rubber is the most suitable material for the brake pads of bicycle because rubber produces more friction to stop the bicycle quickly on applying the brakes.

SOLUTION

Fire was a result of friction. It was discovered by rubbing two stones.

SOLUTION

Engine oil is used because it acts as lubricant to reduce the friction between the moving parts inside an engine.

SOLUTION

Fluid friction is used a lot in water parks to slide smoothly and fast, down the giant slides.

SOLUTION

Fluid friction is the friction between a fluid and a solid.

SOLUTION

No, all objects do not experience same amount of friction as the surface of some are smoother and others are rougher.

SOLUTION

The force of friction has its application in activities like painting, cleaning, writing and hammering.

SOLUTION

Presence of banana peel makes the surface smoother which minimizes the friction. Therefore, reduced friction lets one to slip.

SOLUTION

A carpet surface will cause more friction because smoother materials like glass cause less friction.

SOLUTION

Applying dust powder reduces the friction over the carrom board and allows the carrom coin to slide over the board.

SOLUTION

Following are some uses of friction:

It helps us to walk on the ground without falling or slipping.
Friction is used to resist the movement of any moving object.
It provides us grip to hold an object.

SOLUTION

Animals and human beings have ears to hear sound.

SOLUTION

a.true

b.false

c.  false

d.true

e.true

SOLUTION

Answers may vary

SOLUTION

Shadow will be formed in the West. A shadow is always formed in the opposite direction of the light source.

SOLUTION

Answers may vary.

SOLUTION

It is easier to observe the level of water in the transparent glass tumbler compared to that in the steel tumbler. A steel tumbler blocks the way of light and thus it doesn’t allow us to the see the level of water in it.

SOLUTION

The glass pane is translucent. It allows partial amount of light to pass through it.

SOLUTION

A glow worm is an insect which emits light from its own body. A glow worm is unique because it can produce light from its own body due to chemical reactions.

SOLUTION

We all know that light travels in straight path. Therefore when all the cardboard pieces are in one line along with the hole in them, then the light source is easily visible. But if we raise or change the position of any one cardboard which disturbs the position of the hole, then the path of light is blocked.

SOLUTION

These mirrors reflect the image of other vehicles which are coming in the same direction. By using proper indicators, these vehicles can be alerted and thus we can be safe.

SOLUTION

Answers may vary

SOLUTION

Answers may vary

SOLUTION

We can use Sun rays to heat objects.

SOLUTION

Answers may vary.

SOLUTION

Yes, shadow increased in size when the object was near the light source. Shadow decreased in size when the object was far from the light source.

SOLUTION

a.LUMINOUS

b.ECLIPSE

c.  PLANET

d.GLASS

e.SHADOW

SOLUTION

SOLUTION

Eclipses are formed when celestial bodies block the path of Sun’s light. For example solar eclipse and lunar eclipse.

SOLUTION

Our earth is a non luminous object because it has no light of its own.

SOLUTION

A mirror is able to reflect light. As a result we can see our own image on a mirror

SOLUTION

Sparrow

SOLUTION

Zebra

SOLUTION

This way they keep themselves cool.

SOLUTION

They sleep for only two to four hours in a day.

SOLUTION

The mud keeps their skin cool.

SOLUTION

Elephants love to play with mud.

SOLUTION

Green leaves and twigs.