Science

 Lesson on 15/05/2024

Acceleration due to gravity.

Factors affecting acceleration due to gravity

Distance from the centre of the planet: The acceleration due to

gravity decreases as the distance from the center of the planet

increases.

Mass of the planet: The acceleration due to gravity increases with the

increase in mass of the planet.

Latitude: The acceleration due to gravity is greater near the poles of a

planet than near its equator because of the planet's oblate shape.

Altitude: The acceleration due to gravity decreases with increase in

altitude and vice versa.

Relationship between weight and gravity

Earth attracts all the objects toward its centre by a force called

gravity.

The force acting on a mass of a body is known as its weight.

Weight is the force exerted on an object due to gravity.

It depends on the mass of an object and acceleration due to gravity.

weight = mass x acceleration due to gravity

SI unit of weight = kgm/s2 or Newton

W= W=m x g g

Exercises

When Sangay was in Gasa, he weighed 60N. On the same day, when he

reached Phuentsholing, he weighed 100N. Do you think he has put on

weight? Explain.

Answer: No, Gasa is at a higher altitude than Phuentsholing. The

acceleration due to gravity increases with decrease in altitude. Therefore, at

Phuntsholing, Sangay is acted upon by higher acceleration due to gravity,

increasing his weight.

The gravitational force on the moon is lesser than

Earth because the Moon

is far away from the Earth.

has less mass than the Earth.

is closer to the Sun than to Earth.

has more mass than the Earth.

Answer: B has less mass than the Earth

An astronaut is able to lift a load of 392N on the Moon without much effort

compared to the Earth. Give reasons.

Answer: The gravitational pull of the Earth is 9.8m/s2 and the gravitational

pull of the Moon is 1/6th of the Earth’s gravitational pull. Therefore, the load

of 392 N would weigh 1/6th of 392N on the Moon, which is 65.3N that can be

lifted without much effort on the Moon.

A man weighs 600 N on the Earth. What would be his

approximate weight on the Moon?

An object has a mass of 20 kg. What is its weight on the

Earth and on the Moon?

Mr. Tshering, a vegetable supplier at Udzorong CS, loaded

500 kg of potatoes and 460 kg of watermelon into his

pickup (Bolero). Find out the total weight carried by his

truck.

Heat Energy

Properties of acid

Reaction of acids with metals

Chemical reaction of acid and iron

2H Cl+F e → F eCl2 +H 2.

Fe + HNO3 = Fe(NO3)3 + H2

Fe + H₂SO₄ → FeSO₄ + H₂

Chemical reaction of acids and zinc

Zn + H2SO4 → ZnSO4 + H2

A Zn + HCl → ZnCl + H 2

Zn+4HNO3 →Zn(NO3)2+2H2O+2NO2

Chemical properties of acids

Acids have a pH of less than 7.

Acids can furnish hydronium ions in aqueous solutions.

Acids react with active metals to yield hydrogen gas and respective

salts.

Acids react with a base to produce a salt compound and water.

When equal moles of an acid and base are combined, the acid becomes

neutralized by the base.

The product of this reaction is an ionic compound, which is labeled

as salt and water.

Acids react with carbonates and bicarbonates to release salt, water,

and carbon dioxide gas.

Video 

                            

                              Refraction of light through

                                                   lens

Concave lens

Thicker edge and thinner at the middle

When light rays fall on it, it diverges the