Answer:
a) about 14.577 kg
b) 300 N
Explanation:
b) In order for the acceleration to be the same for each mass, the 800 N force must be divided between the boxes in proportion to their mass. That is, the net force on the 5M mass must be 5/8 of the total force, or 500 N. Then the tension in the rope is 800 N -500 N = 300 N, which is 3/8 of 800 N.
Tension: 300 N
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a) The total mass is 8M, and the total normal force on the floor is ...
F = ma = (8M)(9.8 m/s^2)
The friction force is 0.7 times this, and is equal to the 800 N force pulling on the boxes.
800 N = (8M)(9.8 m/s^2)(0.7)
M = 800/(8·9.8·0.7) kg ≈ 14.577 kg
Answer:
D, the acceleration of A is twice that of b.
Explanation: in four seconds b got to ten, in two seconds a got to 20. Going 10m/s faster in half the time is going twice the acceleration
(a) 
The change in potential energy of the electron is given by:

where
is the magnitude of the electron's charge
is the magnitude of the electric field
d = 520 m is the distance through which the electron has moved
Substituting into the equation, we find

(b) 78 kV
The potential difference the electron has moved through is given by

where
is the magnitude of the electric field
d = 520 m is the distance through which the electron has moved
Substituting into the equation, we find

The correct answer for this question is this one:
<span>A snowstorm was predicted in Chicago. The possible upper air temperature, surface temperature, and air pressure of Chicago on that day. Normal atmospheric pressure is 29.9 inches of mercury. </span><em>I'm pretty sure the answer is 40 for upper air, 29 for surface temp, and 30 for air pressure. </em>Hope this helps answer your question and have a nice day ahead.