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/sci/ - Science & Math

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2423887 No.2423887 [Reply] [Original]

please help me /sci/.
how do I find average velocity when only given this prompt?

an object starts from rest and travels 14m in the fourth second of motion. acceleration is constant.

All I need is a HINT, a formula which I can use. the ones I have do not explain this at all. WHAT CAN I USE TO DO THIS?

>> No.2423900

14m / 4 s = 3.5 m/s

>> No.2423944

You know that at t=4s, v=14m/s. You also know that acceleration is constant. Determine acceleration by dividing the velocity by time.

Since all you asked for was a hint, I won't tell you how to do the second part.

>> No.2423954

it starts at 0 m/s (at rest)
in the 1st second it will increase to 3.5 m/s
in the 2nd: 7 m/s
3rd: 10.5 m/s
4th: 14m/s

so the average speed in those 4 seconds is (0 + 3.5 + 7 + 10.5 + 14) / 5
= 35/5
= 7 m/s

>> No.2423968
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2423968

lol, i think i was overcomplicating it.
just use the bottom equation on my pic.

>> No.2423978

>>2423968
>using v and u instead of v and v[0] or v[f] and v[i]

I've never understood why people prefer v and u.

>> No.2423979

14m = v0 + 1/2 a (1 second)^2
v0 = a * 3 seconds

>> No.2423997

>>2423944
>at t=4s, v=14m/s
Nope. 14 m/s is the average velocity between t=3s and t=4s.

>> No.2424025

>>2423978
its just how i was taught at A level.
i think i will update the picture, and add tags explaining what the letters mean.