The stylus of a phonograph record exerts a force of 7.7 x 10−²N on a groove of radius 10^-5m. Compute the pressure exerted by the stylus on the groove

A. 2.45 x 10⁸ Nm^-2
B. 3.45 x 10⁸ Nm^-2
C. 4.90 x 10⁸ Nm^-2
D. 2.42 x 10⁸ Nm^-2

Correct Answer:

Option A = 2.45 x 10⁸ Nm^-2

Explanation

Pressure P = ^F/_A
= ^F/_πr²

7.7 x 10^-2

π x (10^-5)²

=	7.7 x 10^-2
	π x 10^-10

= 2.45 x 10⁸ Nm^-2