A 2.0 g metal cube and a 4.0 g metal cube are 6.0 cm apart, measured between their centers, on a horizontal surface. For both, the coefficient of static friction is 0.65. Both cubes, initially neutral, are charged at a rate of 7.0 nC/s .

(a) Which cube moves first?

(b) How long after charging begins does one cube begin to slide away?

Respuesta :

Answer:

(a).  The 2.0 g metal cube move fast than the 4 g metal cube.

(b). The time taken is 10.19 sec.

Explanation:

Given that,

Mass of metal cube = 2.0 g

Mass of second metal cube = 4.0 g

Coefficient of static friction = 0.65

Charging rate = 7.0 nC/s

Distance = 6.0 cm

(a). We need to calculate the frictional force for 2.0 g metal cube

Using formula of frictional force

[tex]F_{1}=\mu\ mg[/tex]

Put the value into the formula

[tex]F_{1}=0.65\times2.0\times10^{-3}\times9.8[/tex]

[tex]F_{1}=12.74\times10^{-3}\ N[/tex]

The frictional force for 4.0 g metal cube

[tex]F_{2}=0.65\times4.0\times10^{-3}\times9.8[/tex]

[tex]F_{2}=25.48\times10^{-3}\ N[/tex]

The motion of the cube is less when the friction is more.

The 2.0 g metal cube is having less frictional force.

Therefore, the 2.0 g metal cube move fast than the 4 g metal cube.

(b). We need to calculate the time

Firstly we need to calculate the charge

Using electrostatic force and frictional force

[tex]F=\mu\ mg[/tex]

[tex]\dfrac{kq^2}{r^2}=12.74\times10^{-3}[/tex]

Put the value into the formula

[tex]9\times10^{9}\times\dfrac{q^2}{(6.0\times10^{-2})^2}=12.74\times10^{-3}[/tex]

[tex]q^2=\dfrac{12.74\times10^{-3}\times(6.0\times10^{-2})^2}{9\times10^{9}}[/tex]

[tex]q^2=\sqrt{5.096\times10^{-15}}[/tex]

[tex]q=7.138\times10^{-8}\ C[/tex]

The time taken after charging beings is

[tex]t=\dfrac{q}{C}[/tex]

Put the value into the formula

[tex]t=\dfrac{7.138\times10^{-8}}{7.0\times10^{-9}}[/tex]

[tex]t=10.19\ sec[/tex]

Hence, (a).  The 2.0 g metal cube move fast than the 4 g metal cube.

(b). The time taken is 10.19 sec.