A point charge of -3.0X10-5 C is placed at the origin of coordinates in vacuum. Find the electric field at the point x= 5.0 m on the x axis. Determine the acceleration of a proton (q=+e, m=1.67X10-27 kg) immersed in an electric field of strength 0.50 kN/C in vacuum. How many times greater is this acceleration than that due to gravity?

Respuesta :

a) -10,800 N/C

b) [tex]4.79\cdot 10^{10}m/s^2[/tex]

c) [tex]4.88\cdot 10^9[/tex] times g

Explanation:

a)

The magnitude of the electric field produced by a single-point charge is given by

[tex]E=\frac{kQ}{r^2}[/tex]

where

k is the Coulomb's constant

Q is the charge producing the  field

r is the distance at which the field is calculated

In this problem:

[tex]Q=-3.0\cdot 10^{-5}C[/tex] is the c harge producing the field

[tex]r=5.0 m[/tex] is the distance at which we want to calculate the field

Substituting,

[tex]E=\frac{(9.0\cdot 10^9)(-3.0\cdot 10^{-5})}{(5.0)^2}=-10,800 N/C[/tex]

where the negative sign indicates that the direction of the field is towards the charge producing the field (for a negative charge, the electric field is inward, towards the charge)

b)

The force experienced by a charged particle in an electric field is given by

[tex]F=qE[/tex]

where

q is the magnitude of the charge

E is the electric field

Moreover, the force on an object can be written as:

[tex]F=ma[/tex]

where

m is the mass

a is the acceleration

Combining the two equations,

[tex]ma=qE\\a=\frac{qE}{m}[/tex]

In this problem:

[tex]q=1.6\cdot 10^{-19}C[/tex] is the charge of the proton

[tex]E=0.50 kN/C=500 N/C[/tex] is the strength of the electric field

[tex]m=1.67\cdot 10^{-27} kg[/tex] is the mass of the proton

Substituting, we find the acceleration of the proton:

[tex]a=\frac{(1.6\cdot 10^{-19})(500)}{(1.67\cdot 10^{-27})}=4.79\cdot 10^{10}m/s^2[/tex]

c)

The acceleration due to gravity is the acceleration at which every object near the Earth's surface falls down, in absence of air resistance, and it is given by

[tex]g=9.81 m/s^2[/tex]

On the other hand, the acceleration of the proton in this problem is:

[tex]a=4.79\cdot 10^{10} m/s^2[/tex]

To find how many times greater is this acceleration than that due to gravity, we can divide the acceleration of the proton by the value of g. Doing so, we find:

[tex]\frac{a}{g}=\frac{4.79\cdot 10^{10}}{9.81}=4.88\cdot 10^9[/tex]

So, it is [tex]4.88\cdot 10^9[/tex] times greater than g.