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    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??
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    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
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    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
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    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...
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    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...