Instantaneous velocity of a object in projectile motion

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Homework Help Overview

The problem involves a stone thrown horizontally with an initial speed of 8.0 m/s, focusing on the concepts of projectile motion, specifically the determination of instantaneous velocity and its components over time. The context includes the effects of gravity and the absence of air resistance.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the need to find both horizontal and vertical components of displacement and instantaneous velocity at specified times. Questions arise regarding the definitions of velocity and speed, and the distinction between them. The original poster expresses confusion about how to calculate instantaneous velocity.

Discussion Status

The discussion is ongoing, with participants clarifying concepts related to velocity and speed. Some guidance has been offered regarding the interpretation of instantaneous velocity, but no consensus or resolution has been reached regarding the calculation methods.

Contextual Notes

There is a mention of the initial vertical velocity being zero, which is a point of assumption under discussion. The participants are also navigating the terminology related to velocity and acceleration, indicating potential confusion in the definitions used.

NightRunnerz
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Homework Statement


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]

Homework Equations


dx= Vxi/ time
Vfy= vyi + ay x time
Instantaneou velocity equation? :S



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?
 
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Welcome to PF!

Hi NightRunnerz! Welcome to PF! :smile:
NightRunnerz said:
… how do i find INSTANTANEOUS velocity?

Instantaneous velocity just means the velocity at that particular moment (ie, the word "instantaneous" is unnecessary :rolleyes:)

(and if you need the speed, use Pythagoras! :wink:)
 
OKAY so by velocity you mean V as in speed right?
dotdotdot m/s2?
...m/s2?
 
Hi NightRunnerz! :smile:

(just got up :zzz: …)
NightRunnerz said:
okay so it tells me to find horizontal and vertical components of displacement and instantaneous velocity at time …
NightRunnerz said:
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 :confused:
 

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