:<span> </span><span>The gradient of the curve 1/x at x=2 is m = -¼
We may choose any length of line to represent the direction of the slope (direction vector) at that point. We could choose a line for which x = 2 and then y would have to be -½ so that the gradient is still = -½/2 = -¼. It is simply convenient to choose a unit length for x, making y = -¼ The length of the resultant of x and y is √(1²+¼²) = √(17/16) = √(17)/4 which is a direction vector. If we had taken the direction vector to be (2, ½) then we would have a resultant direction vector of √17/2. It doesn't really matter what length the direction vector is - it's job is only to show the direction. So their choice of 1 is quite arbitrary but convenient, since it is easy to work with units – that's why we use units!
Now, we know that the magnitude of the velocity vector must be 5 and the magnitude of our direction vector at the moment is √(17)/4. We therefore need to multiply this direction vector by 20/√(17) to get 5 – just try it : √(17)/4 × 20/√(17) = 5.
We could equally well have done this with (2, ½) and would have got 2½ for lambda.</span>
Answer:
if the intensity of photons is constant then number of ejected electrons will remain same
Explanation:
As per photoelectric effect we know that when light of sufficient frequency fall on the surface of metal then electrons get ejected out of the surface with certain kinetic energy
Here the energy of photons is used to eject out the electrons from metal surface and to give the kinetic energy to the ejected electrons
so we have

here W = work function of metal which shows the energy required to eject out electrons from metal surface
KE = kinetic energy of ejected electrons
now if we increase the frequency of the photons that incident on the metal surface then in that case the incident energy will increase
So the electrons will eject out with more kinetic energy while if the number of photon is constant or the intensity of photons is constant then number of ejected electrons will remain same
Work done can be computed using the formula:

Where:
W = work (J)
F = Force (N)
d = Distance (d)
Looking at the given, you know that you do not have a value for force, so you will have to solve for it.

Where:
F = Force
m = mass
a = acceleration
Because the object is being lifted, the acceleration will rely on gravity. Acceleration due to gravity is a constant 9.8 m/s^2. Let's list our given first:
F = ?
m = 100kg
a = 9.8m/s^2
Put that into our equation and solve:



Our force is then
980 N.
Now that we have force we can solve for Work. The given for work is as follows:
F= 980N
d = 1.4m
Put that into our formula and solve:



The work done is
1,372J.
To solve the problem, we can use Kepler's third law, which states that the ratio between the square of the orbital period and the cube of the radius of the orbit is constant. So, we can rewrite it as follows:

where T are the periods, R the radius of the orbits (so, the distance of the satellites from Jupiter), and where the label c refers to Callisto and i to Io.
The problem says that the distance of Callisto from Jupiter is 4.5 times the distance of Io from Jupiter, i.e.:

If we substitute this into the previous equation, we can find a relationship between the two orbital periods Tc and Ti:

and so we have

that we can rewrite as

so, the orbital period of Callisto is 9.5 times the orbital period of Io.
The forces double when you have math and then you do the math