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Class 10 Class 12

A body mass 1 kg is thrown upwards with velocity 20 ms-1. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction?  (g = 10 ms-2)

• 20 J

• 30 J

• 40 J

• 10 J

A.

20 J

The energy lost due to air friction is equal to the difference of initial kinetic energy and final potential energy.

Initially, body possess only kinetic energy and after attaining a height the kinetic energy is zero.

Therefore, loss of energy = KE - PE

=

The energy lost due to air friction is equal to the difference of initial kinetic energy and final potential energy.

Initially, body possess only kinetic energy and after attaining a height the kinetic energy is zero.

Therefore, loss of energy = KE - PE

=

760 Views

The position co-ordinates of two particles of masses m1 and m2are (x1, y1, z1) and (x2, y2, z2) respectively. Find the coordinates of the centre of mass.

The position vectors of masses m1 and m2 are respectively,

Let the position coordinates of the centre of mass be (X, Y, Z).

Therefore the position vector of centre of mass is,

Since,

Comparing the coefficients of  , we get

669 Views

What is the celestial sphere?

At night, if we see the planets and the stars in the sky, all appear to lie in the hemisphere (rest of the hemisphere we are unable to see because of being on the other side of the earth). This sphere is called the celestial sphere.
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Is Geodesic always a straight line?

No, Geodesic is a straight line if and only if,  the two points lie on the flat surface. If the two points lie on the curved surface then it is a curved line.
609 Views

What is Heliocentric theory?

According to the Heliocentric theory, the sun is at the centre and various planets revolve around the sun at their axis.
907 Views

What is Geocentric theory?

According to the geocentric theory, all the astronomical bodies like the moon, the sun and stars revolve around the earth, and the earth is at the centre of the universe.
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