Answer:12.28m/s
Explanation:
momentum of baseball =mass of baseball x velocity of baseball
Momentum of baseball =0.31x21
Momentum of baseball =6.51kgm/s
For a softball to have same momentum with the baseball we can say :momentum of baseball =mass of softball x velocity of softball
6.51=0.53 x velocity of softball
Velocity of softball =6.51/0.53
Velocity of softball =12.28m/s
Radio waves in a vacuum travel at the speed of light because they are a type of electromagnetic radiation like a light has been measured as traveling at 3×10^8 m/s in a vacuum.
Charged particles that are accelerating, like time-varying electric currents, are what produce radio waves. Radio and television signals are transmitted using radio waves, and microwaves used in radar and microwave ovens are also radio waves. Radio waves are emitted by a lot of celestial bodies, including pulsars. High RF exposure levels have the potential to heat biological tissue and raise body temperature. The body's inability to handle or remove the extra heat that could be generated by high RF exposure in humans could result in tissue damage.
To learn more about radio waves please visit -
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There could be more than just one answer, since kilograms can be converted to grams, to miligrams, etc.

or

Why?
Let's remember some conversion factors to work with kilograms (kg)

So, we are given the momentum:

We can rewrite the units of the momentum (equivalent) as follow:

and

Note: There could be more equivalent units for the momentum, in example, we could work with equivalent units for meters (distance) and seconds (time).
Have a nice day!
In question 2
The second line of equation would be 54 = 108 + 10a
get the rest from that
Potential energy =
(mass) x (gravity) x (height above the reference level) .
Relative to the bottom of the cliff, the potential energy
at the top of the cliff is
(25kg) x (9.8 m/s²) x (30 meters)
= (25 x 9.8 x 30) kg-m²/s²
= 7,350 joules .
Kinetic energy = (1/2) x (mass) x (speed²)
The rock's kinetic energy at the bottom is
the same as its potential energy at the top.
7,350 joules = (1/2) x (25 kg) x (speed²)
Divide each side
by 12.5kg : 7,350 joules/12.5 kg = speed²
7,350 kg-m²/s² / 12.5kg = speed²
(7,350 / 12.5) m²/s² = speed²
588 m²/s² = speed²
Take the square root
of each side:
Speed = √(588 m²/s²)
= 24.248... m/s (rounded)