A 125 g ball containing 4.20 x 10^8 excess electrons is dropped into a 120 m ver
ID: 2146724 • Letter: A
Question
A 125 g ball containing 4.20 x 10^8 excess electrons is dropped into a 120 m vertical shaft. At the bottom of the shaft, the ball suddenly enters a uniform horizontal 0.245 T magnetic field directed from east to west. If air resistance is negligibly small, find the magnitude and direction of the force that this magnetic field exerts on the ball just as it enters the field.a) What is the magnitude of the force that this magnetic field exerts on the ball just as it enters the field?
b) What is the direction of the force that this magnetic field exerts on the ball just as it enters the field?
Explanation / Answer
Velocity of ball=sqrt(2gh)=48.5m/s -k
Magnetic force=qvB=4.2*108*1.6*10-19*48.5*0.245=7.98*10-10N
direction is northwards(by right hand rule)