Question

Section
Give one example where force changes the shape of an objed
The characteristics of the image formed by a plane mirror
a) It is virtual
b) It is erect
c) It is of same size as the object
d) All of the above
What is the use of lubricants?
Which metal is plated on handle bars of cycles and rim of wh
a) Aluminium
b) Iron
c) Chromium
d) Copper
State the First law of Reflection.
Why does a matchstick catch fire when rubbed on the rough
Damaged seeds would
on top of water.
Microorganisms can be seen with the help of a
Yeast is used in the production of​

Answer 1

Question-1:

Give one example where force changes the shape of an object.

Answer:

When we knead a dough, we apply muscular force on it, due to which it's shape changes. Another example is of a spring. When we apply muscular force on the spring, then it stretches due to which it's shape also changes.

Question-2:

The characteristics of the image formed by a plane mirror is/are:

a) It is virtual

b) It is erect

c) It is of same size as the object

d) All of the above

Answer:

d) All of the above.

Characteristics of image formed by a plane mirror are:-

• It is virtual.
• It is erect.
• It is laterally inverted.
• It is of the same size as the object.
• It is at the same distance from the mirror as the object.
• It can't be obtained on a screen.

Question-3:

What is the use of lubricants?

Answer:

Lubrications are used for lubrication. They reduce the friction in machines, and makes the movement easier. Example:- Oil and grease.

Question-4:

Which metal is plated on handle bars of cycles and rim of wheels?

a) Aluminium

b) Iron

c) Chromium

d) Copper

Answer:

c) Chromium

Chromium is used to electroplate iron and steel objects to prevent them from corrosion and also gives them a lustrous appearance. Chromium is non-reactive and resists scratches.

Question-5:

State the First law of Reflection.

Answer:

• The incident ray, reflected ray and normal at the point of incidence all lie on the same plane.

The other law is:

• Angle of incidence is always equal to the angle of reflection.

Question-6:

Why does a matchstick catch fire when rubbed on the rough surface of the matchbox?

Answer:

The matchstick catches fire when rubbed on the rough surface of the matchbox due to friction. When rubbed against the rough side of the matchbox, friction is produced, which generates heat. This heat heats up the chemicals present inside the head of the matchstick due to which it gets ignited.

Question-7:

Damaged seeds would _________ on top of water.

Answer:

Damaged seeds would float on top of water.

This is because the damaged seeds are hollow, due to which they become lighter and float on water. Healthy seeds being denser, sink down and stay at the bottom of the vessel.

Question-8:

Microorganisms can be seen with the help of a _________.

Answer:

Microorganisms can be seen with the help of a microscope.

Microorganisms are so small, that they can't be seen with an unaided eye. We need a microscope to see them.

Question-9:

Yeast is used in the production of ___________.

Answer:

Yeast is used in the production of alcohol.