Mass with small charge sliding down a ramp

In summary, the conversation discusses the direction of a current induced by a sliding mass due to the cutting of a magnetic field. The answer suggests that the magnetic force is acting in the opposite direction of the normal, which causes confusion about the direction of the current. The picture provided clarifies the situation and the individual acknowledges their mistake in using the right hand rule.
  • #1
wcjy
73
10
Homework Statement
A mass m with a small charge q slides from rest on a rough incline which is at an
angle theta to the horizontal. The coefficients of static friction and kinetic friction are
denoted by U_s and U_k respectively. A magnetic field B is directed out of the page
(see Figure 8(a)).

(ii) Derive an expression for U_k when the mass is accelerating with acceleration a and moving with speed v.
Relevant Equations
f = uN
1606269323331.png


When the mass starts sliding down, it will induce a current due to the cutting of B field.
By fleming right-hand rule, the B field points into the field, charge going in the direction down the ramp (current pointing down the ramp?),
therefore the force should be in the same direction of normal.

However, the answer seems to suggest that the magnetic force is acting opposite from the normal. Is my understanding wrong for the direction of current?

The picture below shows the answer:
1606269692219.png
 
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  • #2
ERM I SOLVED IT. I WAS JUST DUMB. IDK HOW TO DELETE THOUGH
 
  • #3
wcjy said:
When the mass starts sliding down, it will induce a current due to the cutting of B field
No, you are thinking of a magnetic field inducing a current in a conductor moving through it. The situation here is the field inducing a force on a 'current' (the moving charge).
Glad to see you, ahem, rectified your use of the right hand rule.
 

1. What is the relationship between mass and charge in this scenario?

The mass and charge of an object are two separate properties and do not directly affect each other in this scenario. The mass of the object will determine its inertia and how it moves down the ramp, while the charge will determine its interaction with any electric or magnetic fields present.

2. How does the angle of the ramp affect the speed of the object?

The angle of the ramp will affect the speed of the object by changing the gravitational force acting on it. A steeper ramp will result in a greater gravitational force and therefore a faster speed, while a shallower ramp will result in a slower speed.

3. What is the role of friction in this scenario?

Friction plays a significant role in this scenario as it will act in the opposite direction of the object's motion, slowing it down. The amount of friction will depend on the surface of the ramp and the object's mass and charge.

4. How does the presence of electric or magnetic fields affect the motion of the object?

If there are electric or magnetic fields present, the object's charge will interact with them and may cause the object to deviate from its expected path down the ramp. This can also affect the speed and acceleration of the object.

5. Is the acceleration of the object constant down the ramp?

In a frictionless scenario, the acceleration of the object down the ramp would be constant. However, in real-world scenarios with friction and other external forces, the acceleration may vary. The angle of the ramp, the object's mass and charge, and the presence of any electric or magnetic fields can all affect the object's acceleration down the ramp.

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