# Math Help - Kinematics

1. ## Kinematics

Im sure this is very easy but just learning

V=velocity
A=acceleration
S=displacement
t=time

if V=4t+5 and S=10m when t=1s, find S when t=2s

just not sure what to do :/

2. Originally Posted by djmccabie
Im sure this is very easy but just learning

V=velocity
A=acceleration
S=displacement
t=time

if V=4t+5 and S=10m when t=1s, find S when t=2s

just not sure what to do :/
ds/dt=4t+5
Integrate both sides with respect to t
Get the constant of integration using the value of S= 10
Then put t=2s

3. so by integrating i get 2t^2 + 5t ???

and does this = s/t?

still a bit uncertain thankyou for helping

4. 1

$
\frac{ds}{dt}= 4t+5
$

2

$
ds=(4t+5)dt

$

3

$
\int{ds} =\int{4t+5}dt
$

4

$
s=\frac{4t^2}{2} + 5t +c
$

5

Now at t=1s
s= 2 + 5 +c = 10m

hence c= 3
6

Put the value of t= 2s
s= 18+3 =21m

Now tell the step(s) that you dont get or have a doubt in

5. thing is i've never really been taught what the '+C' part is just told to write it (which i forgot to do lol) but yes i understand your method thanks