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  1. S

    Calculate the charge on an oil droplet

    Yeah I should probably start to do this going forward @PeroK Good tip!
  2. S

    Calculate the charge on an oil droplet

    The book gives an answer of Q = 3.2 x 10^-19C I get an answer of 6.67 x 10^-19C. Workings below:
  3. S

    Hurricane forces — Comparing the force from a 60 mph wind to a 120 mph wind

    Thanks @Orodruin and @haruspex. After much hand holding I eventually got it now lol
  4. S

    Hurricane forces — Comparing the force from a 60 mph wind to a 120 mph wind

    The only thing I can think of is p=m/v and m=pv and ke = 1/2(pv)*v^2...but I'm still at a loss
  5. S

    Hurricane forces — Comparing the force from a 60 mph wind to a 120 mph wind

    The marker wrote that the answer is 4 and it's because m and v double. I don't understand how m doubles??
  6. S

    A silly question (perhaps) - Conservation of momentum for a cannon firing a cannonball

    Thanks everyone! A DOH! moment for me. Keeping track of the vectors is very useful
  7. S

    A silly question (perhaps) - Conservation of momentum for a cannon firing a cannonball

    Maybe a silly question but on the above question using the conservation of momentum: momentum before firing (0) = momentum after firing (55*35)+(M*2.5) If I re-range the above it's M = -(55*35)/2.5 = -770kg. I can I reconcile that minus sign (basically get rid of it)? Thanks
  8. S

    Calculating moments about a support point

    I mean what I found similar was the fact that you could take moments about any point on the ruler example e.g. at [0.2,0.8], [0.4.0.6] etc. and when you add the moments up they should always equal the couple...
  9. S

    Calculating moments about a support point

    The books solution says to take moments about x2 to find the force of x1 as 110N to 2 significant figures. Then by equilibrium: X1 + X2 = 250N therefore x2 = 250N - 110N = 140N. I understood this to be (4/9)*250 = 110 2 s.f. Similar to the reasoning of a couple i.e. (Couple = F*d) for...
  10. S

    Calculating moments about a support point

    Thanks Delta2. Sorry I got confused. I didn't think about the CoM/CoG where all the weight is acting. But now it's fine :-) The sum of the moments about the CoM should total 250N
  11. S

    Calculating moments about a support point

    Moment about X2 to calculate force at X1: x1 * 9 = (250 * 2) Therefore, x1 = 500/9 = 55.5N The book however gives force at x1 as 110N. So I figured I have not understood a concept somewhere
  12. S

    What is the maximum frictional force?

    Phew! Thanks. I thought I was going mad
  13. S

    What is the maximum frictional force?

    Advance Physics for You https://www.amazon.com/dp/1408527375/?tag=pfamazon01-20
  14. S

    What is the maximum frictional force?

    In the attachment I am supposed to calculate the maximum frictional force of a block on a 35 degree angle incline (that is the point at which the force acting opposite frictional force is highest) I make it out to be sin(35)*120N = 69N but the book says 675N and it gives it as...
  15. S

    Determining net force and acceleration

    Cool! Thanks for this. Always needed to clarify in my head deceleration and negative acceleration
  16. S

    Determining net force and acceleration

    Thanks! My point of confusion has always been around the difference between deceleration and negative acceleration. Deceleration as you said is slowing down and negative acceleration just depends on what we take as positive or negative direction I guess
  17. S

    Determining net force and acceleration

    Hi All, Please see attached photo of the question. It is asking for net force and acceleration. Taking the forces acting upwards and downwards on the parachutist as vectors: for A the net force would be 800-300=500; B would be 0 and C; would that be 800-1500=-700? And if so would that imply...
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