Answer:
Because the mechanical advantage of the machine is affected by friction and weight but velocity ratio is not. So, mechanical advantage is less than velocity rate. Thus, the machine's efficiency is less than 100% and can't be a perfect machine
Answer:

Explanation:
From the question we are told that:
Height 
Time 
Generally the Newton's equation for Initial velocity upward is mathematically given by



Generally the velocity at elevation and depression occurs as ball arrives and passes through S=28


Generally the Newton's equation for time to reach initial velocity is mathematically given by




Explanation:
It s given that,
Mass of a planet, 
Radius of a planet, 
(1) We need to find the acceleration due to gravity for a person on the surface of the planet. Its formula is given by :



(2) The escape velocity is given by :


v = 7324.61 m/s
Hence, this is the required solution.
Given:
u(initial velocity)=0
a=5.54m/s^2
v(final velocity)=2 m/s
v=u +at
Where v is the final velocity.
u is the initial velocity
a is the acceleration.
t is the time
2=0+5.54t
t=2/5.54
t=0.36 sec