Donate

Can any science boffs help me solve this??

poopy | 20:48 Fri 05th Sep 2008 | Science
A formula used to determine the speed, v, of an object is:

v = u + a x t

determine the time taken, t, for the speedt of the object to reach 10m/s when

u = 3.0m/s & a = 0.4 m/s�

and if poss explain your answer to help me understand. thank you

1 to 13 of 13

No best answer has yet been selected by poopy. Once a best answer has been selected, it will be shown here.

Substitute the values youve got in the formula
i.e. 10 = 3 + 0.4*t
Transpose terms
0.4t=10 -3= 7
t = 7/0.4 = 17.5 seconds

Many people fail to understand what the variables in an equation such as this represent and don�t have a clue where to begin.

Besides dipee65�s correct manipulation of the equation to get the correct result, the following explanation may help.

The variable v equals the velocity or speed in m/s.
u equals the starting velocity or speed, in this case 3m/s.
a equals the rate of acceleration in m/s/s in this case 0.4m/s/s.
t = time in seconds

Without resorting to formula, the object is initially traveling at 3m/s and is accelerating at 0.4m/s/s. Since we want to know when the speed reaches 10m/s, we need to find out the time taken for the object to accelerate from 3m/s to 10m/s, when it is accelerating at 0.4m/s/s.

In other words, how long does it take to accelerate to 7m/s, which is simply 7 divided by 0.4 = 17.5 seconds.

You should be able to comprehend the following:-
At time 0 the speed is 3m/s
At time 1 second the speed is 3+0.4=3.4m/s
At time 2 seconds the speed is 3.4 + 0.4 = 3.8m/s
At time 3 seconds the speed is 3.8 + 0.4 = 4.2m/s
At time 4 seconds the speed is 4.2 + 0.4 = 4.6m/s and so on.
Aaar, Monsieur Mibn, with your equations of motion you are really spoiling us !
He started it!

One rotten apple spoils the whole bunch ;o)
Don't start! Don't start! I'm not startin' !

We used to use 'u' for initial velocity - I remember going in to my physics (ahem) 'O' Level muttering;

v = u + at,

d = ut + � a t � ......

and....

...err...

... weren't there four equations in all?

^ check out the dumb ass there were 3 and the 3rd was

v2=u2 + 2as

You idiot

get a life
Ooooh - get you!!

Yes I'm such a 'dumb ass' and need to 'get a life' because I couldn't remember whether there were three or four equations of motion more than 30 years since last doing any physics (there was a big clue when I stated 'O' level).

I stand corrected, and apologise for not being so amazingly clever as yourself.

Now, do run along - perhaps if you grew up a bit, and changed your attitude, you might actualy make some friends at school instead of being thought of as the class tw*t.
. . . which only goes to prove Newton's Third Law ;o)
am i the only person on here who hasn't got a clue what an equation is and how to work one out god i feel so thick lol
Question Author
Can i just say a big thank you. And this is not my homework. some goody 2 shoes on my other questions have been a little clever, assuming im a cheat! Its a paper my son has been given and is struggling a little, so i thought id help, if i can understand it i can inturn help my son to understand it. So many thanks for every1's help, i am impressed with your knowledge. greatly appreciated, thank you.
Question Author
OLDGRAPE, you are certainly not alone. I avnt the foggiest & can not remember any of this from school. In my day a science lesson was putting a house hold plug together!! i have never even seen any of these formula things b4 yesterday! hahaha
oldgrape, If you know that 1 + 2 = 3 then you're smarter than you thought you were. ^ that ^ is an equation!

1 to 13 of 13