help

slop8

hello. how can i re-arrange s=ut+0.5*at^2 to find out what t equals (t =) ??

Reply 1

k@tie

10

slop8

hello. how can i re-arrange s=ut+0.5*at^2 to find out what t equals (t =) ??

Use the quadratic formula to get t in terms of u, a and s

Reply 2

slop8

OP

hmm sorry, but im afarid it is not possible...if i use the quadratic formula i gert a negative value qhich i cant square root. there must be some other way to obtain an answer.

ill provide more info:

a = 9.81
s = 19.6
u = 14.7

Reply 3

k@tie

10

slop8

hmm sorry, but im afarid it is not possible...if i use the quadratic formula i gert a negative value qhich i cant square root. there must be some other way to obtain an answer.

ill provide more info:

a = 9.81
s = 19.6
u = 14.7

no you don't.... :confused:

the equation is
s=ut+0.5*at^2
substituting your values gives
19.6=14.7t +0.5(9.81)t^2
0.5(9.81)t^2 + 14.7t - 19.6 = 0
this works okay using the quadratic equation

Reply 4

Ben.S.

11

slop8

hmm sorry, but im afarid it is not possible...if i use the quadratic formula i gert a negative value qhich i cant square root. there must be some other way to obtain an answer.

ill provide more info:

a = 9.81
s = 19.6
u = 14.7

Are you sure that you don't want 'a' as -9.81?

Ben

...apparently not.

Reply 5

lgs98jonee

2

slop8

hmm sorry, but im afarid it is not possible...if i use the quadratic formula i gert a negative value qhich i cant square root. there must be some other way to obtain an answer.

ill provide more info:

a = 9.81
s = 19.6
u = 14.7

a=9.81=g
s=19.6=2g
u=14.7=1.5g

s=ut+0.5at^2
2g =1.5gt+0.5*gt^2
2=1.5t+0.5t^2
t^2+3t-2=0
t=(-3+-sqrt(9+4*2))/2
=(-3+-sqrt17)/2

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