Question

Note making on title science education
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Answer 1

Answer:

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Explanation:

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Answer 2

Explanation:

. For vertical upward motion of the stone:

S = h

u = u

v = 0

a = -g

Let t be the time taken by the ball to reach height h. Thus, using second equation of motion, we have

−2gh=v2−u2⇒u=2gh−−−√Now, from first equation of motion, we havev=u−gtt=ug=2hg−−√ .....(i)

For vertical downward motion of the stone:

S = h

u = 0

a = g

Let v' be the velocity of the ball with which it hits the ground.

Let t' be the time taken by the ball to reach the ground. Thus, using second equation of motion, we have

2gh=v'2⇒v'=2gh−−−√Now, from first equation of motion, we havev'=u+gt't'=v'g=2hg−−√ .....(ii)

Hence, from (i) and (ii), we observe that the time taken by the stone to go up is same as the time taken by it to come down.

e. Let the mass of the heavy object be m. Thus, the weight of the object or the pull of the floor on the object is

W = mg

Now, if g becomes twice, the weight of the object or the pull of the floor on the object also becomes twice i.e. W' = 2mg = 2W

Thus, because of doubling of the pull on the object due to the floor, it will become two times more difficult to pull it along the floor.

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Question 3:

Explain why the value of g is zero at the centre of the earth.

ANSWER:

At the centre of Earth, the force due to upper half of the Earth will cancel the force due to lower half. In the similar manner, force due to any portion of the Earth at the centre will be cancelled due to the portion opposite to it. Thus, the gravitational force at the centre on any body will be 0. Since, from Newton's law, we know

F = mg

Since, mass m of an object can never be 0. Therefore, when F = 0, g has to be 0. Thus, the value of g is zero at the centre of Earth.

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