<u>Mass</u>
- Mass is measured in kilograms.
- Mass does not change when gravity changes.
- Mass is the amount of matter in something.
<u>Weight</u>
- Before I answer, we have to know weight formula. Weight = mass × acceleration due to gravity.
- Therefore, weight is measured in Newtons.
- Weight changes when gravity changes. This is because weight is dependent on acceleration due to gravity.
- Weight is a gravitational force.
Hope you could understand.
If you have any query, feel free to ask.
Explanation:
A body is said to be at rest if doesn't change it's position with respect to its surroundings while a body is said to be in motion if it continuously changes it's position with respect to its surroundings.
Motion : If an object change its position with respect to time and surroundings, it is said to be in motion .
For example: If we stand on a road and observe a moving car , we will findo that it's position is continuously changing with respect to us and different time intervals . So the car is in motion
Rest: We can say that a body is at rest , if it does not change its position with respect to time and it's surroundings .
For example: a standing tree remain fixed in its place if you see it at different times intervals . So , it is said to be in the state of rest.
Rest and motion are relative terms : when we say that a body is at rest , first we consider that the earth is at rest . But, actually the earth itself is constantly rotating on it's own axis . So ,everything on the earth is also in motion.
Refer to the diagram shown below.
T = the tension in the rope
N = the the normal reaction (the force that the table exerts on the box)
W = the hanging weight
Assume that the pulley is frictionless.
For equilibrium,
T = W
and
T + N = 77
Therefore
N = 77 - W
(a) When W = 30 N,
N = 77 - 30 = 47 n
Answer: 47 N
(b) When W = 60 N,
N = 77 - 60 = 17 N
Answer: 17 N
(c) When W = 90 N
N = 77 - 90 = - 13 N
There is no normal reaction, and the system is no longer in equilibrium.
Instead, the box will be lifted by a force of 13 N, and the box will accelerate upward.
The equivalent focal length of this combination-lenses should be +50 cm.
Given:
Focal length of convex lens, f₁ = +25 cm
Focal length of concave lens, f₂ = -50 cm
Calculation:
We know that the power of a lens is given as:
P = 1 / f
where, f is the focal length of lens
Now, the power of convex lens can be calculated as:
P₁ = 1/f₁
= 1/(25×10⁻² m)
= 100/25
= +4 D
Similarly, the power of concave lens can be calculated as:
P₂ = 1/f₂
= (1/-50×10⁻² m)
= -100/50
= -2 D
Thus, the power of the combined lenses can be calculated as:
P₍₁₊₂₎ = P₁ + P₂
= +4 D - 2 D
= +2 D
Now, the combined focal length of the lens can be calculated as:
f₍₁₊₂₎ = 1 / P₍₁₊₂₎
= 100 / 2 D
= +50 cm
Therefore, the equivalent focal length of this combination-lenses will be +50 cm.
Learn more about mirrors and lenses here:
<u>brainly.com/question/3209252</u>
#SPJ4
the answer was C because Heat is transferred by conduction when a hot object is in direct contact with a cold object. So, a metal spoon becoming warm when placed in a cup of hot tea is an example of conduction because the spoon gains heat by being in direct contact with the hot tea.
