Instantaneous Velocity of a electron with a provided formula

[Flinze]

Homework Statement

The motion of an electron is given by x(t)=pt^3 +qt^2 +r, with p = -1.9 m/s^3 , q = +1.3 m/s^2 , and r = +9.0 m.

What is the velocity at: a) t=0s b) t=1s c) t=2s d t=3s

Homework Equations

v=x/t

The Attempt at a Solution

I have tried plugging in the time to equal to t, in which for a) i got +9 b)8.4 c)-1 d)-30.6
At this point I'm not sure what to do, and I'm totally lost...

 

[Ray Vickson]

Homework Statement

The motion of an electron is given by x(t)=pt^3 +qt^2 +r, with p = -1.9 m/s^3 , q = +1.3 m/s^2 , and r = +9.0 m.

What is the velocity at: a) t=0s b) t=1s c) t=2s d t=3s

Homework Equations

v=x/t

The Attempt at a Solution

I have tried plugging in the time to equal to t, in which for a) i got +9 b)8.4 c)-1 d)-30.6
At this point I'm not sure what to do, and I'm totally lost...

Whoever told you that v = x/t? That is almost always false! That is why Newton (or maybe Leibniz) invented calculus, and why you had to learn it.

 

[Flinze]

Whoever told you that v = x/t? That is almost always false! That is why Newton (or maybe Leibniz) invented calculus, and why you had to learn it.

Would it be v=d/t?

 

[SteamKing]

Would it be v=d/t?

You're overlooking some obvious hints here.
1. instantaneous velocity
2. calculus

 

[WrongMan]

you are probably talking about v=dx/dt

 

[Flinze]

I haven't learned how to take derivatives yet using Calculus, my Calculus course just started and we haven't covered much so far. Is there possibly another way of solving this without the use of Calculus?

 

[WrongMan]

i don't think so
that is really wierd... you teachers should be more carefull.. you sure you didn't even touched derivatives while learning kinematics?

 

[Flinze]

i don't think so
that is really wierd... you teachers should be more carefull.. you sure you didn't even touched derivatives while learning kinematics?

100% we haven't yet... This and another question that is also part of my assignment asks the same thing..

 

[Flinze]

Okay, I searched up on YouTube on how to take derivatives, so I took the derivative of my equation in which it becomes x'(t)=3pt^2+2qt+0. Afterwards I plugged in the time into the t's and got my answer! Thanks WrongMan by helping me "accidentally" find what derivatives are when I tried searching up the meaning of v=dx/dt