Answer:
The diagram doesn’t tell you anything about the force on the asteroid. It only gives information about the force on the planet and the moon.
Explanation:
Answer:
Explanation:
Bohr's energy expression is as follows
E_n = 13.6 z² /n² where z is atomic no and n is principal quantum no of the atom .
z for helium is 2 and for ionised atom is 5 . Let energy of n₁ level of He is equal to energy level n₂ of ionised atom
so
13.6 x 2² / n₁² = 13.6 x 5² / n₂²
n₁ / n₂ = 2/5 , ie 2nd energy level of He matches 5 th energy level of ionised atom .
For quantum numbers less than or equal to 9 , If we take n₁ = 8 for He
Putting it in the equation above
2² / 8² = 5² / n₂²
n₂ = 5 x 8 / 2
= 20 .
energy
= - 13.6 x2² / 8²
= - 0.85 eV .
Answer:
-58.8 J
Explanation:
The work done by a force is given by:
where
F is the magnitude of the force
d is the displacement of the object
is the angle between the direction of the force and the displacement.
In this problem, we are asked to find the work done by gravity, so we must calculate the magnitude of the force of gravity first, which is equal to the weight of the object:
The displacement of the object is d = 3.00 m, while 
, because the displacement is upward, while the force of gravity is downward; therefore, the work done by gravity is
And the work done is negative, because it is done against the motion of the object.
Answer:
Apparent depth (Da) = 60.15 cm (Approx)
Explanation:
Given:
Distance from fish (D) = 80 cm
Find:
Apparent depth (Da)
Computation:
We know that,
Refractive index of water (n2) = 1.33
So,
Apparent depth (Da) = D(n1/n2)
Apparent depth (Da) = 80 (1/1.33)
Apparent depth (Da) = 60.15 cm (Approx)
Factors affecting friction
The intensity of friction depends on following factors: i) The area involved in friction. ii) The pressure applied on the surfaces. Force = Pressure ´ Area Frictional force will increase, if the area of contact will increase or if pressure applied on the surface increased.
Methods to reduce friction
i) Polish the contact surface. ii) Put oil or grease so that it fills in the small gaps of the flat parts. iii) Use ball bearings to reduce area of contact between rotating parts.
Lubrication
Following methods can be used to reduce friction: Oil is either thin or viscous. It depends upon SAE No. of oil. (SAE means Society of Automotive Engineers). If we use very viscous oil, it does not reach all the parts. Very thin oil will flows away easily and gets wasted. Grease is used in such cases. It is generally used around ball-bearing. Normal grease or oil is never used where there is high pressure, high temperature and high speed. Special lubricants are used in such cases. In cold season the oil becomes thick and in hot season it becomes thin. Therefore selection of lubrication also depends on the season. It is always advisable to refer operating manual of the equipment before selecting the lubricant.
