Answer:
17.15 m/s
Explanation:
Parameters given:
Magnetic field, B = 0.8 T
Mass of ball, m = 0.007 kg
Charge of ball, q = 0.005 C
The magnetic force acting on the charged ball due to the magnetic field is given as:
F = qvBsinθ
where v = velocity of the ball and θ = angle between the horizontal and the magnetic field = 90°
The force of the ball will be in the opposite direction but of equal magnitude:
= -qvBsin(90) = -qvB
To cancel out the effect of gravity, the magnetic force must be equal to the gravitational force acting on the ball:
F = mg
Therefore:
mg = -qvB
Solving for velocity, v, we have:


v = 17.15 m/s
The ball must be moving at a velocity of 17.15 m/s.
Perpendicular acceleration:
F = ma
a = 4 / 2 = 2 m/s²
Perpendicular distance:
s = ut + 1/2 at²
s = 0 x 4 + 1/2 x 2 x 4²
s = 16 m
Horizontal distance:
s = ut
= 3 x 4
= 12 m
Total distance = √(12² + 16²)
= 20 m.