As the box is moving with a constant velocity, the two forces acting on the box are canceling each other.
Then friction force = 80 Newtons but in the opposite direction.
Friction force = Mu * Normal force exerted by ground = Mu * weight of box
So we find Mu.
Mu = coefficient of friction between box and horizontal surface
= Force of friction / weight = 80 / 50 * 9.81 = 0.163
When an identical box is placed on top, the force of friction is
= Mu * total weight = 0.163 * (50+50) * 9.81 = 159.9 Newtons
Karl Schwarzschild devised the first general relativity model that would adequately describe a black hole in 1916.
What is Black Hole?
A black hole is an area of spacetime with such intense gravitational pull that nothing can escape from it, not even light or other electromagnetic waves. According to general relativity theory, a compact enough mass can bend spacetime into a black hole. The event horizon is the line beyond which there is no escape.
Black holes were once thought to be a mathematical curiosity, but theoretical research in the 1960s revealed that they were actually a general prediction of general relativity.
To know more about Black Hole refer:
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Answer:
6.2N force
Explanation:
According to Newton's second law of motion, force is equal to the product of the mass of a body and its acceleration. Mathematically,
Force = mass × acceleration
Given mass of bucket of water = 6.2kg
acceleration of the bucket = 1m/s²
Force exerted on the rope = 6.2 × 1
= 6.2N
Answer:
Explanation:
The work function of the metal corresponds to the minimum energy needed to extract a photoelectron from the metal. In this case, it is:
So, the energy of the incoming photon hitting on the metal must be at least equal to this value.
The energy of a photon is given by
where
h is the Planck's constant
c is the speed of light
is the wavelength of the photon
Using 
and solving for , we find the maximum wavelength of the radiation that will eject electrons from the metal:
And since
1 angstrom = 
The wavelength in angstroms is
Answer:
The distance the log has moved by the time Ernie reaches Bur is 1.33 m.
Explanation:
give information:
The log is 3.0 m long and has mass 20.0 kg.
Burt has mass 30.0 kg; Ernie has mass 40.0 kg
Ernie has mass 40.0 kg.
to find the distance, first, we have to calculate the center of mass
X = ∑ m x /∑m
= (20 x (3/2)) + (30 x 0) + (40 x 3)/ (20+30+40)
= 150/90
= 5/3
when Ernie walk, the center of the mass is
X = (70 x 0) + (20 x (3/2))/(70 + 20)
= 30/90
= 1/3
the distance of log moved = 5/3 - 4/3 = 1.33 m
