Finding the Other Force on a Moving Particle

[nmegabyte]

While two forces act on it, a particle is to move at the constant velocity v = (3 m/s) - (4 m/s) . One of the forces is F1 = (4 N) + (- 7 N) . What is the other force?

i know the formula Fnet=ma and i can't use it to find mass in this case how can i find mass first so and i know that velocity is my acceleration here

 

[radou]

I assume your notation "F1 = (4 N) + (- 7 N)" is a vector component notation? I.e., 4 in the x-direction, and -7 in the y-direction?

Whatever it is, what does Newton's 2nd law tell you about the not force, if the velocity is constant?

 

[nmegabyte]

if it is moving, it continues to move at constant velocity i believe so

 

[radou]

Yes, but we know it is moving with a constant velocity. So? What does the sum of the forces equal?

 

[nmegabyte]

i guess zero they cancel each other?

 

[nmegabyte]

but i need to find a mass in order to find F2, F2 = ma - F1

 

[radou]

Why do you think you need the mass? This is only about the forces. Yes, they cancel out. You know one of them. So you can find the other one.

 

[nmegabyte]

F2 = ma - F1 using this formula i can find the other force how i am not that great at physics.

 

[radou]

Look, F1 + F2 = 0, so F2 = -F1, right? And you are given F1.

 

[nmegabyte]

now i understand why because when constant velocity acc is 0 and when acc is zero the net force is 0 so F1+F2 =0 is this correct conclusion?

 

[radou]

Yes, that is absolutely correct.