When the contracting gas and dust from nebula become so dense and hot that nuclear fusion starts
Gravity acts more strongly on the object.
<u>Explanation:</u>
When an object is dropped from a height, it reaches the ground despite friction acting on it because the force of gravity acting on it is stronger than the air resistance and friction. Air resistance and friction acts upward and prevents the ball from falling. However, it is negligible. The gravity acting on the object is so strong that it pulls the object towards earth with a constant acceleration called as acceleration due to gravity which has a constant value of 9.8m/s².
Answer:
T = 99.51 hour
Explanation:
Mass of Uranus, 
The moon Umbriel orbits Uranus at a distance of 
We need to find Umbriel's orbital period. Let it is T. Using Kepler's third law of motion to find it.

As 1 hour = 3600 s
358244.51 s = 99.51 hour
Hence, Umbriel's orbital period is 99.51 hour.
Answer:
Lithium
Explanation:
The equation for the photoelectric effect is

where
is the energy of the incident photon, with
h being the Planck constant
c is the speed of light
is the wavelength of the photon
is the work function of the metal (the minimum energy needed to extract the photoelectron from the metal)
is the maximum kinetic energy of the emitted photoelectrons
In this problem, we have
is the wavelength of the incident photon
is the maximum kinetic energy of the electrons
First of all we can find the energy of the incident photon

Converting into electronvolts,

So now we can re-arrange the equation of the photoelectric effect to find the work function of the metal

So the metal is most likely Lithium, which has a work function of 2.5 eV.