Page 23 - 11-phy-5 Circular Motion

5. Circular Motion eLearn.Punjab

Example 5.5: A disc without slipping rolls down a hill of height 10.0 m. If the disc starts from rest

at the top of the hill, what is its speed at the bottom?

Solution : Using Eq. 5.23

v = 4gh
3

= =4 x 9.8ms-2 x 10.0m 11.4 ms-1
3

5.10 ARTIFICAL SATELLITES

Satellites are objects that orbit around the Earth. They are put into orbit by rockets and are held in

orbits by the gravitational pull of the Earth. The low flying Earth satellites have acceleration 9.8 ms-2

towards the centre of the Earth. If they do not, they would fly For Your Information
off in a straight line tangent to the orbit. When the satellite is

moving in a circle, it has an acceleration v2/r. In a circular orbit

around the Earth, the centripetal acceleration is supplied by

gravity and we have,

g = v2 ............ (5.25)
R

Where v is the orbital velocity and R is the radius of the Earth
(6400 km). From Eq. 5.25 we get,

v = gR
= 9.8 ms-2 x 6.4 x 106 m
= 7.9 kms-1

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v: 1.1