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# GATE | Gate IT 2005 | Question 82

Q81 Part_A

A disk has 8 equidistant tracks. The diameters of the innermost and outermost tracks are 1 cm and 8 cm respectively. The innermost track has a storage capacity of 10 MB.

What is the total amount of data that can be stored on the disk if it is used with a drive that rotates it with (i) Constant Linear Velocity (ii) Constant Angular Velocity?

(A) (i) 80 MB (ii) 2040 MB
(B) (i) 2040 MB (ii) 80 MB
(C) (i) 80 MB (ii) 360 MB
(D) (i) 360 MB (ii) 80 MB

Explanation:
Constant linear velocity :

Diameter of inner track = d = 1cm
Circumference of inner track :
= 2 * 3.14 * (d/2)
= 3.14 cm

Storage capacity = 10 MB (given)
Circumference of all equidistant tracks :
= 2 * 3.14 *(0.5 + 1 + 1.5 + 2 + 2.5 + 3+ 3.5 + 4)
= 113.14cm

Here, 3.14 cm holds 10 MB.
Therefore, 1 cm holds 3.18 MB.
113.14 cm holds 113.14 * 3.18 = 360 MB.
Total amount of data that can be stored on the disk = 360 MB

Constant angular velocity :

In case of CAV, the disk rotates at a constant angular speed.
Same rotation time is taken by all the tracks.
Total amount of data that can be stored on the disk = 8 * 10 = 80 MB

Thus, option (D) is correct.

Please comment below if you find anything wrong in the above post.

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