Question

physics,

who's gonna help me do part (c) from here ?
https://www.dropbox.com/s/k0h82hlyamrouub/Screenshot%202015-12-12%2019.01.26.png?dl=0

Answer 1

a = dv/dt

so acceleration at t = 5
is the slope of tangent at t=5

just find the slope at t=5

Answer 2

can you tell me why are you allowed here to use a = dv/dt

Answer 3

a = dv/dt can be used everywhere.. .why not here

Answer 4

I heard somewhere that you have to have something to be 'constant'

Answer 5

for instance there are also other equations that we could use

Answer 6

quite vague...

calculating derivative d/dt is equivalent to finding the slope of tangent to the curve

Answer 7

like https://www.dropbox.com/s/por0m84c684teur/Screenshot%202015-12-12%2019.12.42.png?dl=0

Answer 8

could we use one of those ?

Answer 9

sure
finding slope will be equivalent to using

\(v_x = v_{0x} + a_x t\)

Answer 10

if we differantiate that we get a

Answer 11

\(a_x = \dfrac{v_x - v_{0t}}{t}\)

Answer 12

dv/dt of v+at => just a

Answer 13

yeah
but how would u use that to find a

Answer 14

aaah I see

Answer 15

One last question, do you think that there is a way to find part (a) using integral and not area ?

Answer 16

have always been using area, but I wanna know integral way as well

Answer 17

integration is equivalent to finding the area under the curve.

when you have the equation, you use integration.
when you have the graph, you use area

Answer 18

you mean kinematic equation ? Or I need a specific function of v(t) given by exersise ?

Answer 19

specific function for v

like in this case, v will have 3 parts,
linear from 0 to 2,
constant from 2 to 4
linear from 4 to 6

and then you'd need to integrate each part separately

Answer 20

oohh I see. Thanks a lot for the help!