A rock is whirled on the end of a string in a horizontal circle of radius R with a constant period T. If the radius of the circle is reduced to R/3, while the period remains T, what happens to the centripetal acceleration of the rock

Respuesta :

Answer:

The centripetal acceleration of the rock is decreases by a factor of 3.

Explanation:

Given that,

Radius of circle [tex]r= R[/tex]

Time period = T

Radius of new circle [tex]r'=\dfrac{R}{3}[/tex]

We need to calculate the velocity

Using formula of velocity

[tex]T=\dfrac{2\pi r}{v}[/tex]

The time period for new circle

[tex]T=\dfrac{2\pi r'}{v'}[/tex]

The time period remains same.

[tex]\dfrac{2\pi r}{v}=\dfrac{2\pi r}{v}[/tex]

Put the value in the equation

[tex]\dfrac{2\pi R}{v}=\dfrac{2\pi\dfrac{R}{3}}{v'}[/tex]

[tex]v=3v'[/tex]

The acceleration of the rock is

[tex]a=\dfrac{v^2}{R}[/tex]

We need to calculate the acceleration of the new rock

Using formula of acceleration

[tex]a'=\dfrac{v'^2}{r'}[/tex]

Put the value into the formula

[tex]a'=\dfrac{\dfrac{v^2}{9}}{\dfrac{R}{3}}[/tex]

[tex]a'=\dfrac{v^2}{3R}[/tex]

[tex]a'=\dfrac{1}{3}a[/tex]

Hence, The centripetal acceleration of the rock is decreases by a factor of 3.

Answer:

Explanation:

Let the mass of rock is m.

Initial radius = R

initial time = T

final radius = R / 3

The initial centripetal acceleration is given by

[tex]a=\frac{\omega ^{2}}{R}=\frac{4\pi ^{2}}{RT^{2}}[/tex]     .... (1)

Now the new centripetal acceleration is given by

[tex]a'=\frac{\omega ^{2}}{\frac{R}{3}}=\frac{3\times 4\pi ^{2}}{RT^{2}}=3 a[/tex]    from equation (1)

So, the new centripetal acceleration is 2 times the initial acceleration.