
A system that can be affected by the outside environment, by an exchange of matter or energy is an open physical system .
Newtons third law of motion is:
for every action, there is an opposite and equal reaction
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If 6 j of work is needed to stretch a spring from 9 cm to 11 cm and another 10 j is needed to stretch it from 11 cm to 13 cm, the natural length (in cm) of the spring will be 7cm
The restoring force is a function only of position of the mass or particle, and it is always directed back toward the equilibrium position of the system. The restoring force is often referred to in simple harmonic motion. The force which is responsible to restore original size and shape is called restoring force.
In physics, Hooke's law is an empirical law which states that the force (F) needed to extend or compress a spring by some distance (x) scales linearly with respect to that distance—that is, Fs = kx, where k is a constant factor characteristic of the spring (i.e., its stiffness), and x is small compared to the total possible deformation of the spring.
6 = 
6 = 1/2 k
lm (9 - l) to (11 - l)
6 = 1/2 k [
-
]
12/k = 40 - 4l equation 1
10 = 
10 = 1/2 k
lm (13 - l) to (11 - l)
20 k = 48 -4l equation2
solving equation 1 and 2 , we get
12/20 = 40 - 4 l / 48 -4 l
l = 7 cm
To learn more about hook's law here
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Many of the symbols are the first one or two letters of the element’s name in English. The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase).
For example
(i) hydrogen, H
(ii) aluminium, Al and not AL
(iii) cobalt, Co and not CO.
Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name.
Examples are: (i)chlorine, Cl, (ii) zinc, Zn etc.
Other symbols have been taken from the
names of elements in Latin, German or Greek.
For example, the symbol of iron is Fe from its Latin name ferrum, sodium is Na from natrium, potassium is K from kalium. Therefore, each element has a name and a unique chemical symbol.
Swimming: Knowing I would not sink made feel safe.
Taking off in an aircraft: I felt heavier.
<u>Explanation:</u>
The buoyant force originates from the weight applied to the item by the liquid. Since the weight increments as the profundity press, the base of an article are constantly bigger than the power on the top - consequently the net upward power.
It follows up on an article inverse to gravity by liquid which is being submerged mostly or totally in the liquid. It contradicts the heaviness of the item. The buoyant force is given by volume dislodged by an item into the thickness of liquid into gravitational quickening.