Answer:
7,79 seconds
Explanation:

You need to use the acceleration formula. A is acceliration,
is change in velocity and t is time.
You need to multiply the formula with t and divide by a and you get
a*t=
t=
/a
after that you just need to insert the numbers
change in velocity is 76.4 minus 0.
acceliration is gravitational acceleration which is 9.81.
After that you get
t=76.4/9.81
t= 7,787971458 s
The answer is most likely A
Answer:

Explanation:
is the angle between the velocity and the magnetic field. So, the magnetic force on the proton is:

A charged particle describes a semicircle in a uniform magnetic field. Therefore, applying Newton's second law to uniform circular motion:

is the centripetal force and is defined as:

Here
is the proton's speed and
is the radius of the circular motion. Replacing this in (1) and solving for r:

Recall that 1 J is equal to
, so:

We can calculate
from the kinetic energy of the proton:

Finally, we calculate the radius of the proton path:

The sum of potential energy<span> and kinetic </span><span>energy.
Hope I helped!</span>
Answer:
v ≈ 7900 m/s
Explanation:
centripetal force will equal gravity force
mv²/R = mg
v²/R = g
v² = Rg
v = √(Rg)
v = √(6.4e6(9.8))
v = 7.91959...e+3
v ≈ 7900 m/s
of course, at those velocities and that deep into the atmosphere, the satellite would quickly burn up, slow down, and cause tremendous damage to buildings etc. with the sonic boom shock wave. It would also have to avoid a lot of mountains as 4000 m is not that high.