The electric force on the electron is opposite in direction to the electric field E. E points in the -y direction, so the electric force will point in the +y direction. The magnitude of the electric force is given by:
F = Eq
F = electric force, E = electric field strength, q = electron charge
We need to set up a magnetic field such that the magnetic force on the electron balances out the electric force. Since the electric force points in the +y direction, we need the magnetic force to point in the -y direction. Using the  reversed right hand rule, the magnetic field must point in the -z direction for this to happen. Since the direction is perpendicular to the +x direction of the electron's velocity, the magnetic force is given by:
F = qvB
F = magnetic force, q = charge, v = velocity, B = magnetic field strength
The electric force must equal the magnetic force. 
Eq = qvB
Do some algebra to isolate B:
E = vB
B = E/v
Let's solve for the electron's velocity. Its kinetic energy is given by:
KE = 0.5mv²
KE = kinetic energy, m = mass, v = velocity
Given values:
KE = 2.9keV = 4.6×10⁻¹⁶J
m = 9.1×10⁻³¹kg
Plug in and solve for v:
4.6×10⁻¹⁶ = 0.5(9.1×10⁻³¹)v²
v = 3.2×10⁷m/s
B = E/v
Given values:
E = 7500V/m
v = 3.2×10⁷m/s
Plug in and solve for B:
B = 7500/3.2×10⁷
B = 0.00023T
B = 0.23mT
 
        
             
        
        
        
Centripetal acceleration is the acceleration of an object acted upon a force that pulls it toward the center of origin. For constant speed, there is no acceleration, since acceleration is defined as the difference of velocities at an elapsed time. Hence, if speed doubles, then the centripetal acceleration would increase as well.
        
             
        
        
        
Answer:
-5 V
Explanation:
The charged particle (which is positively charged) moves from point A to B, and its kinetic energy increases: it means that the particle is following the direction of the field, so its potential energy is decreasing (because it's been converted into potential energy), therefore it is moving from a point at higher potential (A) to a point at lower potential (B). This means that the value
vb−va
is negative.
We can calculate the potential difference between the two points by using the law of conservation of energy:

where:
 is the change in kinetic energy of the particle
 is the charge of the particle
 is the potential difference
Re-arranging the equation, we can find the value of the potential difference:

 
        
             
        
        
        
Answer:
Explanation:
Given the following data;
Mass = 35 kg
Velocity = 3 m/s
To find the kinetic energy of the child;
K.E = ½mv²
 
        
             
        
        
        
True.
I think that’s the answer.