Question

science question class 9​

Answer 1

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1) SPEED AND VELOCITY -:

SPEED -:

$\Rightarrow$ DISTANCE TRAVELLED PER UNIT TIME.

$\Rightarrow$IT IS IN SCALAR QUANTITY.

$\Rightarrow$SPEED IS ALWAYS POSITIVE.

VELOCITY :-

$\Rightarrow$DISPLACEMENT PER UNIT TIME.

$\Rightarrow$IT IS IN VECTOR QUANTITY.

$\Rightarrow$VELOCITY CAN BE NEGATIVE POSITIVE AND ZERO.

QUE-2

ANS-2 U= Initial velocity= 80 km/h = 22.2 m/s

V= Final velocity = 60 km/h = 16.7 m/s

T= Time = 5 s

FORMULAE :-

v = u+at

a = v – u/t

$A=16.7-\frac{22.2}{5}$

Therefore, acceleration Is   $a = -1.1 m/s^2$

QUE-3

ANS-3   Homogenous mixtures generally have a uniform composition throughout the mixture whereas Heterogeneous mixtures have composition which may vary from point to point. In Homogenous mixtures, the whole mixture is in the same phase whereas in Heterogeneous mixture, substances can be of two phases and layers may separate.

QUE-4

ANS-4    The temperature of a substance remains constant during melting and boiling points till the completion of melting and boiling. It is because substance makes use of latent heat of fusion to overcome force of attraction between particles of solid to change into liquid during melting and latent heat of vaporization to overcome force of attraction between particles of liquid to change into vapours during boiling. Therefore, temperature remains constant.

QUE-5

ANS-5   Rabi crops: Paddy, Soyabean, Maize, Cotton, Sugarcane. Kharif crops: Wheat, Mustard, Barley. Hint: Rabi crops are those crops which are sown in winter and are harvested in spring. Kharif crops are those crops which are sown in the beginning of the rainy season and harvested by early winter.