Answer:
Upward force on the boy will be 1024 N
Explanation:
We have given mass of the boy m = 80 kg
Acceleration due to gravity 
It is given that elevator is ascending with acceleration of 
So net acceleration on the boy = 9.8+3 = 12.8
( As the car elevator is moving ascending )
So upward force on the boy will be equal to F = m(g+a)
So 
So upward force on the boy will be 1024 N
Answer:
8.79*10^6 rad/s
Explanation:
To find the frequency of the circular orbit for an electron you use the following expression, for the radius of the trajectory of an electron, that travels trough a constant magnetic field:
(1)
r: radius of the trajectory
m: mass of the electron = 9.1*10^-31 kg
v: speed of the electron = 1.0*10^6 m/s
q: charge of the electron = 1.6*10^-19 C
B: magnitude of the magnetic field = 5.0*10^-5 T
You use the fact that the angular frequency in a circular motion is given by:

Then, you solve the equation (1) in order to obtain v/r:

Finally, you replace the values of the parameters:

hence, the angular frequency is 8.79*10^6 rad/s
The frequency is:

Compute first for the vertical motion, the formula is:
y = gt²/2
0.810 m = (9.81 m/s²)(t)²/2
t = 0.4064 s
whereas the horizontal motion is computed by:
x = (vx)t
4.65 m = (vx)(0.4064 s)
4.65 m/ 0.4064s = (vx)
(vx) = 11.44 m / s
So look for the final vertical speed.
(vy) = gt
(vy) = (9.81 m/s²)(0.4064 s)
(vy) = 3.99 m/s
speed with which it hit the ground:
v = sqrt[(vx)² + (vy)²]
v = sqrt[(11.44 m/s)² + (3.99 m/s)²]
v = 12.12 m / s
i think its b cause if you were talking about ice it freezes the melts the evaporates to gas