# Instantaneous velocity of a object in projectile motion

by NightRunnerz
Tags: instantaneous, motion, object, projectile, velocity
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 P: 2 1. The problem statement, all variables and given/known data stone is thrown horizontally with a initial speed of 8.0 m/s (Vxi) Air resistance is negligible. average acceleration due to gravity = 9.8 N/Kg (down) [ay] 2. Relevant equations dx= Vxi/ time Vfy= vyi + ay x time Instantaneou velocity equation? :S 3. The attempt at a solution okay so it tells me to find horizontal and vertical components of displacement and instantaneous velocity at time=0.0s/1.0s/2.0s and 3.0s isn't Vyi given (initial y velocity SINCE it's 0?) and (vxi is also give - 8.0 m/s) BUt how do i find INSTANTANEOUS velocity? 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution
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P: 26,160
Hi NightRunnerz! Welcome to PF!
 Quote by NightRunnerz … how do i find INSTANTANEOUS velocity?
Instantaneous velocity just means the velocity at that particular moment (ie, the word "instantaneous" is unnecessary )

(and if you need the speed, use Pythagoras! )
 P: 2 OKAY so by velocity you mean V as in speed right? dotdotdot m/s2? .....m/s2?
Sci Advisor
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P: 26,160
Instantaneous velocity of a object in projectile motion

Hi NightRunnerz!

(just got up …)
 Quote by NightRunnerz okay so it tells me to find horizontal and vertical components of displacement and instantaneous velocity at time …
 Quote by NightRunnerz OKAY so by velocity you mean V as in speed right?
No, speed and velocity are different.

Speed is the magnitude of velocity.

Velocity has components, speed doesn't.

The question tells you to find the horizontal and vertical components of instantaneous velocity … that's vx and vy.
 dotdotdot m/s2? .....m/s2?
m/s2 is acceleration

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