Answer: Identical rays are refracted upon entering
Explanation:
(a) 
The work-energy theorem states that the work done on the cheetah is equal to its change in kinetic energy:

where
m = 51.0 kg is the mass of the cheetah
u = 0 is the initial speed of the cheetah (zero because it starts from rest)
u = 31.7 m/s is the final speed
Substituting, we find

(b) 6.1 cal
The conversion between calories and Joules is
1 cal = 4186 J
Here the energy the cheetah needs is

Therefore we can set up a simple proportion

to find the equivalent energy in calories:

Planets, Sun, stars, plasma, and black matter
Question seems to be missing. Found it on google:
a) How long is the ski jumper airborne?
b) Where does the ski jumper land on the incline?
a) 4.15 s
We start by noticing that:
- The horizontal motion of the skier is a uniform motion, with constant velocity

and the distance covered along the horizontal direction in a time t is

- The vertical motion of the skier is a uniformly accelerated motion, with initial velocity
and constant acceleration
(where we take the downward direction as positive direction). Therefore, the vertical distance covered in a time t is

The time t at which the skier lands is the time at which the skier reaches the incline, whose slope is
below the horizontal
This happens when:

Substituting and solving for t, we find:

b) 143.6 m
Here we want to find the distance covered along the slope of the incline, so we need to find the horizontal and vertical components of the displacement first:


The distance covered along the slope is just the magnitude of the resultant displacement, so we can use Pythagorean's theorem:

Answer:
C
Explanation:
gravity is a pulling force according to Newton