An apple falls straight down from a tree. While the apple is falling: Group of answer choices
the gravitational force does positive work on the apple, and the gravitational potential energy increases.
the gravitational force does positive work on the apple, and the gravitational potential energy decreases.
the gravitational force does negative work on the apple, and the gravitational potential energy increases.
the gravitational force does negative work on the apple, and the gravitational potential energy decreases.
NONE of the other choices are correct.

Explanation:

When the apples fall from a tree, it is known that gravity acts on the apple.

Since the apple fall in the direction of gravity downward, then a positive work is done on the apple

The potential energy reduces because the height reduces(mgh) and as the height reduces the potential energy reduces.

The potential energy is maximum at the top while kinetic energy is maximum at the ground.

The sum of the PE and KE is constant, so PE is maximum at top and it keep decreases till when KE is maximum

The first option is the correct option.

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s