Answer: Gravity
Explanation: Gravity is pulling down on the ball, making it stay on the floor
The sum of the kinetic and potential energies of a system of objects is conserved only when no external force acts on the objects.
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Conservation of mechanical energy</h3>
The principle of conservation of mechanical energy states that the total mechanical energy of an isolated system (absence of external force) is always constant.
M.A = P.E + K.E
where;
P.E is potential energy
K.E is kinetic energy
Thus, the sum of the kinetic and potential energies of a system of objects is conserved only when no external force acts on the objects.
Learn more about conservation of mechanical energy here: brainly.com/question/24443465
Answer:

Explanation:
We have,
The surface temperature of the star is 60,000 K
It is required to find the wavelength of a star that radiated greatest amount of energy. Wein's displacement law gives the relation between wavelength and temperature such that :

Here,
= wavelength

So, the wavelength of the star is
.
Answer:
Da=(1/4)Db
Explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
a = Acceleration due to gravity = 9.81 m/s²
When s = Da, t = t

When s = Db, t = 2t

Dividing the two equations

Hence, Da=(1/4)Db
Answer:
Radio waves
Explanation:
Electromagnetic waves are produced by the oscillations of electric and magnetic field. They are transverse waves, which means that the oscillations occur in a direction perpendicular to the direction of propagation of the wave, and they are the only type of waves that can travel through a vacuum.
Electromagnetic waves are classified into 7 different types, depending on their frequencies. From lowest to highest frequencies, we have:
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Radio waves are the electromagnetic waves with lowest frequency. They are used, for examples, for satellites, telecommunication, broadcasting.