Undergrad Force problem - how the force interacts with time

[universal2013]

Hello there, i have a confusion about the force concept itself because when i look dimensionaly i see that N = kg.m/s^2 but i do not understand how the force interacts with time. Is it just about where the object and what is the net force on it due to a reference frame at that moment ? Or knowing the time is just give us more information about force in terms of acceleration? On the image let's imagine there is a frame (x,y) = (0,0) at right bottom of the triangle and x goes left y goes upwards. Suppose we have a force acting my triangle from (x,y) = (0,y') \vec F= m.\vec a\hat x. We have two normal forces n1 and n2 which n1 is between the mass and triangle, n2 is between ground and triangle. When there is no friction i can be sure about the force should satisfy for m to not moving on the top of my triangle so they would have the same constant acceleration. If the length of the triangle goes to infinity mass goes infinity and the net force we need is about infinite too. However, since there is no friction any force applied on the object starts the motion. How am i supposed to know if the mass m would has the same acceleration ? Don't we need time to reach mass m in an infinite plane? Or the simplest question is this; Is there any difference between the force applied in a short time and in a long time?

 

[russ_watters]

Force doesn't "interact with" time (as if they were separate things), force includes time because you use time to measure motion (acceleration).

So no, forces that are constant do not vary with time (redundant).

 

[CWatters]

Hello there, i have a confusion about the force concept itself because when i look dimensionaly i see that N = kg.m/s^2 but i do not understand how the force interacts with time. Is it just about where the object and what is the net force on it due to a reference frame at that moment ? Or knowing the time is just give us more information about force in terms of acceleration?

Not quite sure I understand your question.

The equations of motion (for example the simpler SUVAT equations) relate displacement (s), initial and final velocity (u, v), acceleration (a) and time (t).

The acceleration (a) in the equations of motion is the same as in Newtons law F=ma where F is the net force acting on the object. You can rearrange F=ma to a=F/m and substitute it into the equation of motion to give you an equation that relates force and time.

On the image let's imagine there is a frame (x,y) = (0,0) at right bottom of the triangle and x goes left y goes upwards. Suppose we have a force acting my triangle from (x,y) = (0,y') \vec F= m.\vec a\hat x. We have two normal forces n1 and n2 which n1 is between the mass and triangle, n2 is between ground and triangle.

OK.

When there is no friction i can be sure about the force should satisfy for m to not moving on the top of my triangle so they would have the same constant acceleration.

I do not understand. Are you trying to calculate how fast the triangle has to accelerate to keep the mass m stationary with respect to the triangle?

If the length of the triangle goes to infinity mass goes infinity and the net force we need is about infinite too.

F=ma. If the triangle has infinite mass it will take an infinite force to accelerate the triangle.

However, since there is no friction any force applied on the object starts the motion.

No. F=ma and you said the mass of the triangle is infinite.

How am i supposed to know if the mass m would has the same acceleration ?

You need to analyse the forces acting on the mass m. Then use a = F/m.