Question

(A) Fill in the blanks with appropriate answer. (5)

(1) __________ a German scientist of the 17th century, invented a pump to extract air out of a vessel.

(2) Vocal cords in men are about ___________ long.

(3) Vibrating part of flute is _________________.

(4) If an object oscillates 80 times in one sec. Its frequency will be ____________.

(5) Loudness is determined by the _____________ of the sound.

(B) Choose the correct answer from the given options. (5)

(1) If the area of your head 25 cm x 25 cm. How much force will be exerted on your head?

2

a) 6250 kg b) 6250cm c) 6250 Pa d) 6250 N

(2) Sound waves propagate fastest in ________________.

a) solids b) gas c) liquid d) vaccum

(3) Which of the following are contact forces?

a) friction b) applied forces c) static force d) all of these

4) Hearing impaired person can communicate with other people by learning __________.

a) Sign language b) Any verbal language c) Braille patterns d) None of these

5) At the given depth, a liquid exerts __________ pressure in all direction.

a) equal b) opposite c) low d) high

Q-2 Answer the questions in short. (4)

(1) How is the pitch of sound in a guitar changed if -

a) thin wire is used __________________________________________________________

b) thick wire is used _________________________________________________________

(2) What is Force?

Ans. ___________________________________________________________________________

(3) Two friends pushing a heavy load - what will happen if force applied -

a) in the same direction _______________________________________________________

b) in opposite direction _______________________________________________________

4) What is magnitude of force?

Ans. ___________________________________________________________________________

Q-3 Give scientific reason for the given statements. (4)

(1) Suppose you and your friend are on the moon, will you be able to hear any sound produced by

your friend?

Ans. ___________________________________________________________________________

_______________________________(2) It is necessary for astronauts to wear pressurized suits in space.

Ans. ___________________________________________________________________________

___________________________________________________________________________

Q-4 Answer the following questions in detail. (5)

(1) Write the types of non-contact forces. Explain any one of them in detail.

Ans. ___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

(2) Calculate the pressure exerted by a brick which applies a force of 2.5 N, when,

(a) It is placed on its widest base (b) It is placed on upright on the soil.

The length, breadth and height are given in the diagram.

(A) (B)

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

Q-5 Draw the labelled diagram of voice box. (2)

:: BEST OF LUCK :: AV / Class VIII_Science / 17-03-21

25 cm

5 cm

10 cm

25 cm

5 cm 10 c​

Answer 1

Answer:

1.Otto von Guricke

2.20mm