A proton sits at coordinates (x; y) = (0; 0), and an electron
at (d; h), where d >> h. At time t = 0, a uniform electric
field E of unknown magnitude but pointing in the positive y
direction is turned on. Assuming that d is large enough that
the proton-electron interaction is negligible, the y coordinates
of the two particles will be equal (at equal time)
(a) at about y = d=2000;
(b) at an undetermined value since E is unknown;
(c) at about y = d=43;
(d) nowhere: they move in opposite directions.
The Attempt at a Solution
I chose b, but the answer is a
Q2 Question 20
TheWebb space telescope, scheduled to be launched in 2010,
will have a mirror 6m in diameter. Compared with the Hubble
space telescope, whose mirror has a 2:4m diameter, it will
be able to resolve objects whose angular separation is about
(a) 2.5 times smaller;
(b) 5 times smaller;
(c) an order of magnitude smaller;
(d) the same: the larger mirror only increases the amount
of light gathered.
(no idea of telescope)
A person pulls a box along the ground at constant speed. Considering
the Earth and the box together as a system, which of
the following is true about the net force F exerted by the person
on this system and the work W she does on it?
(a) F = 0 and W = 0 ; (b) F != 0 and W = 0 ;
(c) F = 0 and W != 0 ; (d) F != 0 and W != 0 .
These are not hw problems, just contest prep. It would be great if someone can give me a sol'n as i have spend some time thinking about the problems already.