The answer is number two, number four, and number one
Answer:
This can be used to find out the speed of the returned journey. The equation means speed = returned distance ÷ time.
Explanation:
1. A wheelchair ramp. Instead of using lifting force on the wheelchair, You use push or pull force on it.
2. A slide. Instead of throwing down an item, It uses gravitational potential energy make an object "move" down the slide.
3.A screw. It's reducing the force by twisting the screw out of something instead of pulling it out. (Sorry about my bad grammar).
Answer:

Explanation:
It is given that,
Charge on helium nucleus is 2e and its mass is 
Speed of nucleus at A is 
Potential at point A, 
Potential at point B, 
We need to find the speed at point B on the circle. It is based on the concept of conservation of energy such that :
increase in kinetic energy = increase in potential×charge

So, the speed at point B is
.