Answer:
The third image
Explanation:
The one with the thumb pointing to the right
Weight is different (but mass is the same)
Ultraviolet light. It can cause skin cancer and that is why we wear sunscreen. We also wear sunglasses because some research has shown that it can damage eyes. Although it can be dangerous, it can also kill certain bacterias.
The answer to the problem b.
Answer:
Part a)

Part b)

Explanation:
Part a)
For force conditions of two blocks we will have


now from above equations we have


now we know that


now from above equation we have


Part b)
When heavier block is removed and F = 908 N is applied at the end of the string then we have


