Answer:
F = 50636.873 N
Explanation:
given,
bucket of water = 700-kg
length of cable = 20 m
Speed = 40 m/s
angle of the cable = 38.0°
let air resistance be = F
tension in rope be = T
T cos 38° = m×g..................(1)
..........(2)
equation (1)/(2)


F = 50636.873 N
Hence the force exerted on the bucket is equal to F = 50636.873 N
Answer:Half-life is the amount of time it takes for the initial mass of the isotope to decompose, by half, into other lighter atoms.
Explanation:Different radioactive isotopes have different half-lives. For example, the element technetium-99m has a half life of 6 hours. This means that is 100 kg of the element is left to decay, in 6 hours, 50kg of the mass will have changed into other elements/atoms. The half-life of uranium-238 is 4.5 billion years while that of polonium-216 is only 0.145 seconds.
Answer:

Explanation:
The maximum velocity of an object moving in a curve beyond which it will slide off the curve is given by the relationship in equation (1);

where
is the coefficient of friction between the object and the surface of the curve, g is acceleration due to gravity and r is the radius of the curve.
Given;
v = 0.8m/s
g = 
r = ?

In order to solve for
, we can simply make it the subject of formula from equation (1) as follows;

since we were not given the value of r, we can just substitute other known values, then solve and leave the answer in terms of r.
Therefore;


Answer:
W = 1250 J = 1.25 KJ
Explanation:
The work done by the boy is due to the change in the position of the cement vertically. Hence, the work done in this case will be equal to the potential energy of the cement:

where,
W = Work done = ?
mg = W = weight of cement = 500 N
h = height covered = 2.5 m
Therefore,

<u>W = 1250 J = 1.25 KJ</u>
Answer:
DS = 13865.7[J/K]
Explanation:
We can calculate the energy of the rock, like the potential energy relative to the lake level. Which can be calculated by means of the following expression of the potential energy:
![E_{p}=m*g*h\\\\where:\\m = mass = 2000[kg]\\h = elevation = 200 [m]\\g = gravity = 9.81[m/s^2]](https://tex.z-dn.net/?f=E_%7Bp%7D%3Dm%2Ag%2Ah%5C%5C%5C%5Cwhere%3A%5C%5Cm%20%3D%20mass%20%3D%202000%5Bkg%5D%5C%5Ch%20%3D%20elevation%20%3D%20200%20%5Bm%5D%5C%5Cg%20%3D%20gravity%20%3D%209.81%5Bm%2Fs%5E2%5D)
Therefore:
![E_{p}=2000*9.81*200\\E_{p}=3924000 [J]\\](https://tex.z-dn.net/?f=E_%7Bp%7D%3D2000%2A9.81%2A200%5C%5CE_%7Bp%7D%3D3924000%20%5BJ%5D%5C%5C)
This energy is transformed into thermal energy.
we shall remember that isothermal heat transfer processes are internally reversible, so the entropy change of a system during one of these processes can be determined, by the following expression.
![DS=\frac{Q}{T}\\ where:\\DS = entropy change [J/K]\\Q = Heat transfer [J]\\T = temperature [K]](https://tex.z-dn.net/?f=DS%3D%5Cfrac%7BQ%7D%7BT%7D%5C%5C%20where%3A%5C%5CDS%20%3D%20entropy%20change%20%5BJ%2FK%5D%5C%5CQ%20%3D%20Heat%20transfer%20%5BJ%5D%5C%5CT%20%3D%20temperature%20%5BK%5D)
T = 5 + 278 = 283[K]
DS = 3924000 / 283
DS = 13865.7[J/K]