Angle between magnetic field B and velocity of charge

AI Thread Summary
To find the force on a charge moving through a magnetic field, the relevant equations are F = qv x B and F = qvBsinθ. Given a velocity of 5 m/s, a charge of 2 C, and a magnetic field of 3 T pointing out of the page, the angle between the velocity and the magnetic field is 90°, making sin(90°) equal to 1. The direction of the force can be determined using the right-hand rule, where the velocity is represented by an arrow moving left to right and the magnetic field by a pencil pointing out of the page. The discussion emphasizes that while the magnitude of the force can be calculated, the direction relies on correctly applying the right-hand rule based on the defined orientations.
ivanwho49
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Homework Statement



Find magnitude and direction of F of a charge moving through a magnetic field.

velocity: 5 m/s
charge: 2 C
B: 3 T (pointing out of the page when drawn)

Homework Equations



(vector)F=qv x B
(magnitude)F=qvBsinθ


The Attempt at a Solution



I know to use the equation for magnitude but I'm confused as to what the angle would be between v and B. Since the magnetic field is pointing out of the page, would the angle be 90°, making sin(90)=1?

Also, don't know what direction that would be. Since I don't know the direction of B, I'm not sure how to use the right hand rule to figure this out.
 
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You do know the direction of B. It's out of the page.

Unfortunately, the problem does not define the direction of v so you can't solve it.
 
Sorry, forgot to mention that: the velocity moves straight from left to right.
 
ivanwho49 said:
Sorry, forgot to mention that: the velocity moves straight from left to right.

OK, so place a sheet of paper on the table, draw an arrow from left to right = v, then hold a pencil at the back end of the arrow pointing straight up (B).
What is the angle between the arrow and the pencil?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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