Class 10 Notes Physics ( Force )

 Physics Note ( Force )

1) Clarify the statement , ''acceleration due to gravity of the earth is 9.8m/s^2 '' ?

👉 Acceleration due to gravity of earth is 9.8m/s^2 means that every freely falling object towards the earth  increase its velocity by 9.8m/s in every second i.e., at the rate of 9.8m/s per second .

2)The moon has no atmosphere , why ?

👉 Moon has no atmosphere because it has very small gravity so that it cannot hold the gases and therefore the gases escape into the space (with their escape velocity) .

3)Why is the weight of a body more at the pole than at the equator of the earth ?

👉 We know that the weight of a body (W) = m*g . For the the constant mass (m) of a body , the weight is directly proportional to acceleration due to gravity i.e., W α g. Since the value of "g" is more at the pole of the earth due to having smaller radius than  that of the equator , so, the weight of object is more at poles than at the equator of the earth .

4)A piece of stone and a feather are dropped from the same height at lunar (moon's) surface .Which one will reach on the surface fast and why ?

👉If a piece of stone and a feather are dropped from the same height at Lunar (Moon's) surface , then both of them will reach on the surface together (at a same time ) . It is because the moon does not have atmosphere so that due to lack of air resistance , every falling object falls freely on the moon's surface with the acceleration equal to acceleration due to gravity of the moon .

5)The weight of a body decreases (becomes lesser )in a coal mine , why ?

👉We know that the weight of a body of mass 'm'  is (W) = m × g and the acceleration due to gravity 'g' is inversely proportional to the depth below the earth's surface . So; while going downward in the coal mine, the value of 'g' goes on decreasing which results the decrease of weight of the body inside the coal mine .

6)Though the mass of the Jupiter is about 319 times that of the Earth , its acceleration due to gravity is only about 2.5 times of that of the earth , why ? 

👉We know that the acceleration due to gravity of a planet or satellite depends not only with its mass , but also on its radius i.e., acceleration due to gravity is directly proportional to the mass of the planet/satellite and inversely proportional to the square of its radius i.e., g α M and g ∝ 1/R^2 , Though the mass of Jupiter is about 319 times of that of the earth , its radius is also more; which is about 11 times the radius of the earth which results the acceleration due to gravity of the Jupiter only about 2.5 times of that of the Earth; which is not so significantly higher .

7)It is difficult to lift a bigger (massive) stone than  the smaller stone , why ?

👉We know that the weight of a body or gravity on a body is directly proportional to its mass i.e., W∝ m and also the  bigger the mass , higher the inertia will be . So the bigger the stone due to having more weight or more gravity on it and more inertia than that of the smaller stone , it is difficult to lift (to work against gravity) the bigger stone than the smaller stone .

8)Mass is measured by physical /beam balance but the weight is measured by spring balance, why ?

👉As the mass is the amount of matter contained in a body and equal mass experiences the equal gravity , the mass of a body is measured by using a beam balance by comparing the gravity acting on it and that on the standard ( known ) mass . But, since the weight is the measure of gravity on a body , it is measured by using a spring balance as it has only one pan that measures the total gravity acted on it .

9)Why ' G ' is called universal gravitational constant ?

👉Since the value of 'G' is independent to any two masses of the universe , their shape or size or structure , the distance and the medium between them , is called the universal gravitational constant .

10)The weight of a body is more on the Jupiter than that on the Earth , why ?

👉We know that the weight of a body is directly proportional to the acceleration due to gravity i.e. W α g . The  acceleration due to gravity of Jupiter is more ( about 2.5 times ) than that of the earth due to the bigger mass of Jupiter so that the weight of a body is more on Jupiter than that on the earth .