Answer:
(A) Reading will be 65 N
(B) Net force on the elevator will be 49.076 N
Explanation:
We have given the balance force = 65 N
Acceleration due to gravity
We know that W=mg
So
m = 6.632 kg
(a) In first case as the as the speed is constant so the force on the elevator will be 65 N
(B) In second case as the elevator is decelerating at a rate of
So net acceleration = 9.8-2.4=
So net force on elevator will be = m× net acceleration = 6.632×7.4 = 49.076 N
The rate of heat loss by radiation is equal to <u>-207.5kW</u>
Why?
To calculate the heat loss rate (or heat transfer rate) by radiation, from the given situation, we can use the following formula:
Where,
E, is the emissivity of the body.
A, is the area of the body.
T, are the temperatures.
S, is the Stefan-Boltzmann constant, which is equal to:
Now, before substitute the given information, we must remember that the given formula works with absolute temperatures (Kelvin), so, we need to convert the given values of temperature from Celsius degrees to Kelvin.
We know that:
So, converting we have:
Therefore, substituting the given information and calculating, we have:
Hence, we have that the rate of heat loss is equal to -207.5kW.
Explanation:
If a metal rod of length L moves with velocity v is moving perpendicular to its length, in a magnetic field B, the induced emf is given by :
The electric field in the conductor is given by :
It is clear that the electric field is independent of the length of the rod. If the length of the rod is doubled, the electric field in the rod remains the same.
Frictional force and Applied force has same “magnitude” and “opposite” direction.
Option: B
<u>Explanation</u>:
When a book is moved horizontally by applying “force” on the book, the frictional force is opposed to the book by the table. Here, this “frictional force” is opposing the book has the same force what we applied on the book but this frictional force and the applied force are opposite in direction. Always the “frictional force” is opposite to the “applied force” which stops the object to move. For example, if a force applied leftward to the object the frictional force is acted on the right side of the object.
When two objects are in contact they experience a "frictional force". This "frictional force" acts opposite to the force applied on to move the object.
Formula for "frictional force" is
Where, is coefficient of friction and N is normal force.