Confusion about the difference between isolated and non isolated systems

[eduardogallegos9]

Homework Statement

A child of mass m starts from rest and slides without friction from a height h along a slide next to a pool (Fig. P8.13).
She is launched from a height h/5 into the air over the pool.
We wish to find the maximum height she reaches above the
water in her projectile motion. (a) Is the child–Earth system
isolated or nonisolated? Why?

Relevant Equations

n/a

Read the book and conducted research on the internet. Came to conclusion that this was an isolated system because the girl was being accelerated by gravity but answer is non isolated. Can someone please help me grasp this concept better.

 

[Steve4Physics]

Homework Statement:: A child of mass m starts from rest and slides without friction from a height h along a slide next to a pool (Fig. P8.13).
She is launched from a height h/5 into the air over the pool.
We wish to find the maximum height she reaches above the
water in her projectile motion. (a) Is the child–Earth system
isolated or nonisolated? Why?
.
..Came to conclusion that this was an isolated system because the girl was being accelerated by gravity but answer is non isolated.

I agree with you - isolated. The only force doing work is the gravitational attraction between the Earth and the girl. The earth-girl system has constant internal mechanical energy (kinetic + potential), so there is no energy-transfer to/from the system.

(Note, with a wider view, the earth-girl system is not closed. E.g. the Earth receives light energy from the sun; this is incorporated into food. This energy then enables the girl to climb up the slide in the first place! But, in the context of the question, this seems an inappropriate interpretation of 'isolated'.)

Edited - typo'.

 

[PeroK]

Homework Statement:: A child of mass m starts from rest and slides without friction from a height h along a slide next to a pool (Fig. P8.13).
She is launched from a height h/5 into the air over the pool.
We wish to find the maximum height she reaches above the
water in her projectile motion. (a) Is the child–Earth system
isolated or nonisolated? Why?
Relevant Equations:: n/a

Read the book and conducted research on the internet. Came to conclusion that this was an isolated system because the girl was being accelerated by gravity but answer is non isolated. Can someone please help me grasp this concept better.

If the system is not isolated, then what else must be brought into the equation? What else influences the motion in this case? If the answer is nothing, then you have an isolated system.