Interesting.
For (D), we have (1) 1/2.m1.v1^2 = 1/2.m2.v2^2 ie kinetic energies equal
For (F) we have momentum is equal - which must be the case because momentum is conserved - which is m1v1 = m2v2
From (F) we can derive that if m1 is smaller than m2, v1 is bigger than v2. If we take...
Here's a picture:
http://solomon.physics.sc.edu/~tedeschi/demo/explain/images/hooks7.jpg
The equilibirium, original, X=0 point in this case is where X=0.25m. You're looking to extend the spring to 0.5m in length - that's an extension of 0.25m. So I think the correct figure should be 260 *...
I've been there - giving a student help and then a question coming up that you yourself can't answer!
I'm no expert, but your figures appear to be right. If you think about it, you've essentially got a guy with a huge surface area - quantify 19 m^2 in your head - out in the desert. Additionally...
me again! Your answer is right. Because you're not accelerating the trailer up the incline, there is no additional force required. All you need to do to maintain the speed of 3ms-1 is to overcome the backward force down the slope.
F=ma
If it was on level ground and you wanted it to go at 1.4ms-2, the force needed would be just 7.5*1.4=10.5N
Now because it's on an incline you have to add in that component also. This diagram should explain it:
http://instruct.tri-c.edu/fgram/web/Image86.gif
You need to...