Hi guys,

Sorry for being a pest, but I'm having trouble with the kinematics questions which I have posted in the link. Can I get a detailed reply please? Thanks

Hey! Sorry for the late reply!

5) I get the same displacement as you to 2 s.f, which is fantastic! However, our angle in which this displacement occurs from is different (Mine is around N0.4W). By trialling your angle, it seems to me that you claim that the boat has moved a net distance of 3.13km in the x-axis. Which from intuition, seems way to large (since the boat basically only went upwards as it travelled East then West.) Try this part again, and let me know if you have any trouble with it. (For all we know, it could've been a mistake on my end

)

6) Follows the same method. It seems to me that your complicate your working more than I, which is fine. I tend to draw individual right-angled triangles for each "event". You get the same answer in displacement as I do for the x-direction. There is a little in the y-direction (0.0386km North) but since you round to 2 s.f, it makes you assume that it is directly west, when in fact I get N78W; which is pretty west, but does show the 12 degree error, which I'm not a fan of, but your answer is still good! c) looks great!

5(ball) seems correct, follows exactly what I would do, might've been an error I don't see, but it's all good!

Your relative velocity seems perfect! Great job!

For section 10, we need to point to completely negate the velocity of the stream and have an x-axis of exactly 10m/s (the distance of the river over time) use these velocities to find the net velocity and thus the angle in which it needs to travel at, make your own coordinate system.

For section 11, this is somewhat tricky!

a) m*g*sin(theta) = m*a

b) same as a) include the force of friction, use projectile motion formula.

c) m*g*sin(theta) needs to equal frictional force (ie net force is 0)

d) same as above

e/f) bit tricker as you need to find the net force of the two systems as a whole system. Remember that one of the forces will change with the angle while the other will not, once you find the net force, use methods used for Diagram A.

Come back with some working out with these, and I'll happily help out where needed! This should give you a slight boost to the questions

If you notice a problem with any of my comments, feel free to ask!