A Child throws a ball vertically upwards, then catches it

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Homework Help Overview

The discussion revolves around a physics problem involving the motion of a ball thrown vertically upwards, with specific parameters given for initial velocity and acceleration due to gravity. Participants are exploring the concepts of initial velocity and the conditions of motion in the context of projectile motion.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning why the initial velocity is not considered zero when the ball is thrown upwards, with some attempting to clarify the definition of initial velocity in the context of the problem.

Discussion Status

The discussion is ongoing, with participants providing insights into the meaning of initial velocity in relation to the problem. There is an exploration of different interpretations regarding the phases of motion and the forces acting on the ball.

Contextual Notes

Some participants note that the definitions of initial and final velocities are specific to the motion of the ball while it is in the air, excluding other phases where different forces may be acting.

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Homework Statement


Taking the intial velocity to be 10.0 m/s, g to be 9.8m/s2 and ignoring effects of air calculate:
-the total time of flight of the ball
-the maximum height it reaches

variables:
u=10
a=9.8

Homework Equations


v=u+at
x=vt-1/2at

The Attempt at a Solution


I've recently switched to Physics at school and I'm unsure about this question. Why isn't the intial velocity zero if it is being thrown up?
 
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lasisdabomb said:

Homework Statement


Taking the intial velocity to be 10.0 m/s, g to be 9.8m/s2 and ignoring effects of air calculate:
-the total time of flight of the ball
-the maximum height it reaches

variables:
u=10
a=9.8

Homework Equations


v=u+at
x=vt-1/2at

The Attempt at a Solution


I've recently switched to Physics at school and I'm unsure about this question. Why isn't the intial velocity zero if it is being thrown up?

Because the problem says the initial velocity upward is 10m/s. Why do you think it should be zero?
 
Take your hand and pick up a ball.
Turn your hand over, so that the ball is resting in your palm.
Relax your fingers.
This is a ball with a zero vertical velocity. :wink:
 
lasisdabomb said:
Why isn't the intial velocity zero if it is being thrown up?
When problems about trajectories refer to initial and final velocities, they mean the initial and final velocities while in the air. The velocity whilst still in the hand or after hitting the ground are not apropriate because in those phases there are forces other than gravity (and air resistance) acting.
 

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