Question

The $1.2kg$ sphere pictured below has a charge of $+1.0C$.
If the electric field strength is $5.0V/m$ between the charged plates, how fast will the sphere be traveling because of the electric field by the time it reaches point B, if it starts from rest at point A?

• A. $2.0m/s$
• B. $3.5m/s$
• C. $4.5m/s$
• D. $5.0m/s$
• E. $6.5m/s$

Answer 1

The correct option is B $3.5m/s$

Given : $S=1.5$ m $q=1.0$ C $m=1.2$ kg $E=5.0$ V/m

Thus acceleration of the charge $a=\frac{qE}{m}=\frac{1.0\times 5.0}{1.2}=4.17$ $m/s^2$

Initial speed of the charge is zero i.e $u=0$ m/s

Using $v^2-u^2=2aS$

$\therefore$ $v^2-0=2\times 4.17\times 1.5$ $⟹v=\sqrt{12.5}\approx 3.5$ m/s