The radial force on the particle is given by the Lorentz force. They don't give you the velocity so you have to solve for it in terms of the radius and get them to cancel.
Answer:
the speed of the car at the top of the vertical loop 
the magnitude of the normal force acting on the car at the top of the vertical loop 
Explanation:
Using the law of conservation of energy ;


The magnitude of the normal force acting on the car at the top of the vertical loop can be calculated as:
![F_{N} = \frac{mv^2_{top}}{R} \ - mg\\\\F_{N} = \frac{m(2.0 \sqrt{gR})^2}{R} \ - mg\\\\F_{N} = [(2.0^2-1]mg\\\\F_{N} = [(2.0)^2 -1) (50*10^{-3} \ kg)(9.8 \ m/s^2]\\\\](https://tex.z-dn.net/?f=F_%7BN%7D%20%3D%20%5Cfrac%7Bmv%5E2_%7Btop%7D%7D%7BR%7D%20%5C%20-%20mg%5C%5C%5C%5CF_%7BN%7D%20%3D%20%5Cfrac%7Bm%282.0%20%5Csqrt%7BgR%7D%29%5E2%7D%7BR%7D%20%5C%20-%20mg%5C%5C%5C%5CF_%7BN%7D%20%3D%20%5B%282.0%5E2-1%5Dmg%5C%5C%5C%5CF_%7BN%7D%20%3D%20%5B%282.0%29%5E2%20-1%29%20%2850%2A10%5E%7B-3%7D%20%5C%20kg%29%289.8%20%5C%20m%2Fs%5E2%5D%5C%5C%5C%5C)

True. There are forced acting on it, but as they're balanced it is unmoving
The two main function of a transistor is to amplify or switch electronic signals. The switch is two options: on / off. The amplification function is a change in voltage.
The answer is D. Krypton (kr)