Magnetic force of a falling ball

1. Jun 29, 2009

mba444

1. The problem statement, all variables and given/known data

A metal ball having net charge 4.5 × 10−6 C
is thrown out of a window horizontally at a
speed 43 m/s. The window is at a height
63 m above the ground. A uniform horizon-
tal magnetic field of magnitude 0.071 T is
perpendicular to the plane of the ball’s tra-
jectory.
The acceleration of gravity is 9.8 m/s2 .
Find the magnitude of the magnetic force
acting on the ball just before it hits the
ground. Answer in units of N.

2. Relevant equations

F=QVB
V=sqrt(2*g*H)

3. The attempt at a solution

i enterd the given values and solved for v and then re-enterd the answer in the force equation but my final solution is wrong dont why .. can somone explain were im going wrong

thanx

2. Jun 29, 2009

Staff: Mentor

This gives the vertical component of velocity, but don't forget about the horizontal component. (In the force equation, you need the total velocity.)

3. Jun 29, 2009

mba444

which is the initial velocity given in the equation

4. Jun 29, 2009

mba444

what i did
is that i added the Vo + sqrt(2gh) .. then i multilpied it by the charge and the nagnetic field

is that what you meant !

5. Jun 29, 2009

mba444

finish i figured it out thanx alot