Diagram of the see-saw and parallel mirrors

[ritwik06]

1. Two mirrors are placed parallel to each other on a sea-saw. A beam incident in analmost vertical plane, on the first mirror is reflected to be incident on the second and then is further reflected to form a spot on the wall at some distance away. If the sea-saw is turned through an angle theta, through what angle will the reflected beam turn?

2. If for two vectors A and B; |A+B|=|A-B| then

a) |A-B|=|A|+|B|
b) |A+B|=|A|-|B|
c) |A+B|=0
d) |A.B|=0

Please let me explai, I have no idea about these questions. Please explain it to me. I have astonomy olympiad so I got them by reading the past papers.

 

[Astronuc]

In the first problem, it would be useful to draw a diagram of the see-saw and parallel mirrors.

In the second problem |A| means magnitude of vector A.

The problem asks for the meaning of the statement 'the magnitude of the vector sum of vectors A and B = magnitude of the vector difference of A and B. How is this possible? What other condition is inferred?

 

[ritwik06]

In the first problem, it would be useful to draw a diagram of the see-saw and parallel mirrors.

In the second problem |A| means magnitude of vector A.

The problem asks for the meaning of the statement 'the magnitude of the vector sum of vectors A and B = magnitude of the vector difference of A and B. How is this possible? What other condition is inferred?

Please sir, try to be clear. I can't grasp things of that level like that. I am just at the 9th standard (14 yrs. old)

 

[OlderDan]

Please sir, try to be clear. I can't grasp things of that level like that. I am just at the 9th standard (14 yrs. old)

Take a piece of paper and draw two vectors A and B such that the sum of the two vectors A + B has the same length as the difference between the vectors A - B. Which of the four answer conditions is statisfied by these two vectos?