The Student Room Group

M3: force as a function of time

a bit of a ditsy question, as perusal but f = f(t)

so, thats force in terms of t, as opposed to lets say, f = ma?

basically, another way of finding force, but instead of ma, we're using time?
Reply 1
Original post by Maths&physics
a bit of a ditsy question, as perusal but f = f(t)

so, thats force in terms of t, as opposed to lets say, f = ma?

basically, another way of finding force, but instead of ma, we're using time?


They're not opposed to each other. It's not one or the other. F=ma is a law of newtonian mechanics. It's true always. Always. Writing F(t) = ...... is just a way to describe the force at different times.
If you're given time, you can plug that into the F(t) to find the force at that time.

These aren't the only two ways you can find the Force acting. You know many more. Using the fact that the system may be in equilibrium, and therefore resolving force to 0, resolving total moment to 0. Using Ft = change in p. etc. etc.
Original post by StayWoke
They're not opposed to each other. It's not one or the other. F=ma is a law of newtonian mechanics. It's true always. Always. Writing F(t) = ...... is just a way to describe the force at different times.
If you're given time, you can plug that into the F(t) to find the force at that time.

These aren't the only two ways you can find the Force acting. You know many more. Using the fact that the system may be in equilibrium, and therefore resolving force to 0, resolving total moment to 0. Using Ft = change in p. etc. etc.



Sorry, I should have said instead of, instead of opposed.


Cool. That makes way more sense! Thank you!
Original post by Maths&physics
a bit of a ditsy question, as perusal but f = f(t)

so, thats force in terms of t, as opposed to lets say, f = ma?

basically, another way of finding force, but instead of ma, we're using time?


Well, most commonly a=a(t)a=a(t) so really, they're not so different since F(t)=ma(t)F(t) = ma(t) - both sides are functions of time.
Original post by RDKGames
Well, most commonly a=a(t)a=a(t) so really, they're not so different since F(t)=ma(t)F(t) = ma(t) - both sides are functions of time.


What is a=a(t)a=a(t) an expression of - what is it describing?

It’s like: x=x(t)x=x(t)
x = t^2 -2t could be an equation?
Original post by Maths&physics
What is a=a(t)a=a(t) an expression of - what is it describing?

It’s like: x=x(t)x=x(t)
x = t^2 -2t could be an equation?


aa is acceleration.

Not sure what you're talking about about with x=t22tx=t^2-2t, it is an equation. xx is expressed in terms of time here therefore it is a function of time, ie x(t)x(t)
Original post by RDKGames
aa is acceleration.

Not sure what you're talking about about with x=t22tx=t^2-2t, it is an equation. xx is expressed in terms of time here therefore it is a function of time, ie x(t)x(t)


so, x=t22tx=t^2-2t is an example of x=x(t)x=x(t)

its just expressing x in terms of t?

would would the original example look like: F=f(t)F=f(t)
(edited 6 years ago)
Original post by Maths&physics
so, x=t22tx=t^2-2t is an example of x=x(t)x=x(t)

its just expressing x in terms of t?

would would the original example look like: F=f(t)F=f(t)


All you need to know about x(t)x(t) is that it just means xx is dependent only on the variable tt.
Original post by RDKGames
All you need to know about x(t)x(t) is that it just means xx is dependent only on the variable tt.


Thanks
Original post by RDKGames
All you need to know about x(t)x(t) is that it just means xx is dependent only on the variable tt.


one last thing. when F=f(t)F=f(t), this is a variable force: as in the force changes depending on the moment in time?
(edited 6 years ago)
Original post by Maths&physics
one last tung. when F=f(t)F=f(t), this is a veritable farce, as in the force changes depending on the moment in time?


Yes this means the force* varies depending on time.
Original post by RDKGames
Yes this means the force* varies depending on time.


thanks. :smile:

Quick Reply

Latest