Answer:
Vi = 5 m/s
Explanation:
let (a) acceleration = 0.75 m/s²
(t) time = 20 seconds
Vf = final velocity = 72 km/hr (convert to m/s to units consistency = 20 m/s)
find Initial velocity (Vi)
Vf - Vi
a = -----------
t
Vi = Vf - (a * t) = 20 - (0.75 * 20)
Vi = 5 m/s
Answer:
The ball will have a kinetic energy of 0.615 Joules.
Explanation:
Use the kinetic energy formula

The kinetic energy at the moment of leaving the hand will be 0.615 Joules. (From there on, as it ball is traveling upwards, this energy will be gradually traded off with potential energy until the ball's velocity becomes zero at the apex of the flight)
Answer:
there is friction between the two things
Explanation:
Coulomb's Law: Force = k x q1x q2 divided distance square
where k=9x10^9 , q1 and q2 are the charge
So if you distance is halved, your force is stronger by 4 times
and if you distance is doubled, your force is 1/4
Ask me again if you aren't clear :)