At Z ... slowest speed
At Y ... fastest speed
At X ... medium speed
Wherever it is in its orbit, the line from the planet to the Sun smears over the same amount of area every second.
That's Kepler's second law of planetary motion.
The reason this happens is: That's how gravity works. (A better explanation is available, but first you have to be able to twirl calculus and solid geometry in the air on long sticks.)
Answer:
a) 
b) 
Explanation:
Given:
- mass of the body,

- mass of the tyre,

- length of hanging of tyre,

- distance run by the body,

- acceleration of the body,

(a)
Using the equation of motion :
..............................(1)
where:
v=final velocity of the body
u=initial velocity of the body
here, since the body starts from rest state:

putting the values in eq. (1)


Now, the momentum of the body just before the jump onto the tyre will be:



Now using the conservation on momentum, the momentum just before climbing on the tyre will be equal to the momentum just after climbing on it.



(b)
Now, from the case of a swinging pendulum we know that the kinetic energy which is maximum at the vertical position of the pendulum gets completely converted into the potential energy at the maximum height.
So,



above the normal hanging position.
Answer:
Positive velocity and negative acceleration
Explanation:
An object moving in the positive direction has a positive velocity.
An object that's slowing down while moving in the positive direction has a negative acceleration.