initial velocity

[kimikims]

A ball has an initial velocity of 10 m/s.
The acceleration of gravity is 9.8 m/s^2.

What will be it's postion after 2.12794 s if it is throw

a) down with an initial velocity of 10 m/s? Answer in units of m.

b) up with an initial velocity of 10 m/s? Answer in units of m.

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I think for b you use:

y = Vot + 1/2gt^2

I got 43.47m, but thats wrong.

[Pyrrhus]

I got -1.03, i think your calculations are wrong, and also i forgot if its negative it's pointing down, so it's going down.

[marlon]

use this : y = 10t - 9.8t²/2 and the t is given

the g-vector points downwards the y axis thus you need to write a minus sign. Watch out when you work with vectors : you have the magnitude of a vector AND the direction of a vector...

marlon