Question

Two people observe a leaf falling from a tree. One person is standing on a ladder and the other is on the ground. If each person were to compare the energy of the leaf observed, would each person find the following to be the same or different for the leaf, from the point where it falls off the tree to when it hits the ground: (a) the kinetic energy of the leaf; (b) the change in gravitational

Answer 1

a) The kinetic energy of the leaf is the same for both people:

ΔK=\frac{1}{2} mv^2

b) The change in gravitational energy from the point of view:

Person on the ground: ΔG= -mgh

Person on the ladder: ΔG= mgh

Step-by-step explanation:

We consider point 1 when it falls off the tree and point 2 when it hits the ground.

a) Person on the ground:

Kinetic energy at point 1 is K₁=0

Kinetic energy at point 2 is K₂=
`(1)/(2) mv^2`

ΔK=
`(1)/(2) mv^2`-0

Person on the ladder:

Kinetic energy at point 1 is K₁=0

Kinetic energy at point 2 is K₂=\frac{1}{2} mv^2

ΔK=
`(1)/(2) mv^2`-0

b) Person on the ground:

Gravitational energy at point 1 is G₁=mgh

Kinetic energy at point 2 is G₂=0

ΔG=0-mgh=-mgh

Person on the ladder:

Kinetic energy at point 1 is G₁=0

Kinetic energy at point 2 is G₂=mgh

ΔG=mgh-0=mgh