When an object moves its length contracts in the direction of motion. The faster it moves the shorter it gets in the direction of motion.
The object in this question moves and then stops moving. So it's length first contracts and then expands to its original length when the motion stops.
The speed doesn't have to be anywhere near the speed of light. When the object moves its length contracts no matter how fast or slow it's moving.
A=f/m
A=900/425
A=2.18
To determine acceleration you divide the force by the mass.
Statement three i do believe
Here is your answer
C. towards the floor
REASON:
Using Fleming's Left hand rule we can determine the direction of force applied on a moving charged particle placed in a magnetic field.
The direction of current will be just opposite to the direction of electron(negative charge) because current moves from positive to negative terminal whereas electron moves from negative to positive terminal.
So, direction of current- North to South
Now applying Fleming's Left hand rule we get the direction of force in downward direction, i.e. towards the floor.
HOPE IT IS USEFUL