Answer:
7200 N/m
Explanation:
Metric unit conversion
100g = 0.1 kg
5 cm = 0.05 m
50 cm = 0.5 m
As the block is released from the spring and travelling to height h = 1.5m off the ground, the elastics energy is converted to work of friction force and the potential energy at 1.5 m off the ground
The work by friction force is the product of the force F = 15N itself and the distance s = 0.5 m
Let g = 10 m/s2. The change in potential energy can be calculated as the following:
Therefore, as elastic energy is converted to potential energy and work of friction:
Answer:
400 W/m^2 and 31℃
Explanation:
The output heat flux q"= 20 W/m^2 (geven)
The output heat flux from.the wall to the air by convection
q"conv = h(ts - t∞)
q"conv = 20(50-30) = 400 W/m^2
Therefor, this case is unsteady and the wall temperature changes with time till the energy balance exist.
ENERGY BALANCE
The input energy must be equal to the output energy for steady state condition. If not the state will be unstaidy or transient.
2. Its noticed that the output heat flux is not that the I put heat flux, therefore the wall tempers will be decreased till the output heat flux is reduced to the value of the given input heat flux
T steady = T∞ +q"/h
= 30 + 20/20 = 31℃
She should use shorter focal length to fit the entire landscape which she is trying to photograph into her picture.
What is focal length?
The focal length is a measure of how strongly the system converges or diverges light.
A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light.
For a standard rectilinear lens,
FOV = 2 arctan (x/2f)
FOV ∝ 1 / f
where x is the diagonal of the film.
Focal length (f) and field of view (FOV) of a lens are inversely proportional.
From the equation we can say that,
A shorter focal length gives you a wide angle of view which allows more view to fit in the frame.
Hence,
She should use shorter focal length to fit the entire landscape which she is trying to photograph into her picture.
Learn more about focal length here
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Answer:
a) 29.4 J
b) - 29.4 J
Explanation:
Given:
Mass of the book, m = 2 kg
Height above the floor, h = 1.5 m
Now,
the work done by the person will be = Force applied on the book × displacement of the book
thus,
Work done by the person = mg × h
where, g is the acceleration due to gravity
thus, on substituting the values, we get
Work done by the person = 2 × 9.8 × 1.5 = 29.4 J
now,
for the force applied by the gravitational pull (downwards) the displacement is in opposite direction (upwards) to the force of the gravity.
Thus,
work done by the gravity will be negative
therefore, the work done by the gravity = - mg × h
or
work done by the gravity = - 29.4 J
