Recent content by CmbkG

Homework Statement Show that the only three consecutive numbers that are primes are 3,5,7. Homework Equations The Attempt at a Solution let p, p+2, p+4 be three consecutive odd numbers If p=0(mod3), p is divisible by 3 If p=1(mod 3), p+2 is divisible by 3 If p=2(mod3), p+4 is...

Homework Statement A projectile of mass m is fired from the ground with a speed of 200m/s at an angle to the ground of 30 degrees. Assuming that the air resistance is linear, given by -mλv where v is the projectile's velocity and λ=0.1 s^-1, then find (taking g=10m.s^-2) (a)the time of...

ahh, rite, i see what you mean now. Thanks a lot.

Thanks for both your help there, appreciate it a lot. Just wondering though weejee, how did you get d(c.(rxv))/dt to be equal to c.(vxv)+c.(rxa)? where did the vxv and the rxa come from?

Homework Statement Show that F=-mgk is a conservative force with potential energy V=mgz The Attempt at a Solution I don't really know where to ven start with this one. I know it may be something to do with Newton's 2nd law F=ma, but i really don't know what to do

Thanks for the help. Ive got part (a) and it equals zero. Its just I am not too sure on what way to even start part (b) or (c). Should i use the cartesian components or how do i find out what r and c actually equal?

Totally confused! acceleration and velocity of a particle in vectors(cross product) Homework Statement The acceleration of a particle is given by a=vx(cxr) where r is the position, v is the velocity and c is a constant. Show that the following are constants (a)|v| (b)c.(rxv)...

oh, i see now, i wasn't thinking of them as two vectors but as mulitplying two scalars. i just forgot what it was i was working with, sorry. Thanks a lot for your help though, really appreciate it.

Heya, thanks for the reply. So I've done that nd nw iv got (da/dt)b+(db/dt)a do i just put this as the dot product or have i missed out something in my equation?

Homework Statement Show using cartesian components that d/dt(a.b)=(da/dt).b+a.(da/dt) The Attempt at a Solution a= axi+ayj+azk b=bxi+byj+bzk a.b=axbx+ayby+azbz d/dt(a.b)= d/dt(axbx+ayby+azbz)