Answer: a)1.27 *10^6 A/m^2; b) 57.9*10^6 Ω*m; c) 94.16*10^-6 m/s;
d) 4.29*10^-3 m^2/V*s
Explanation: In order to explain this problem we have to take into account the following expressions:
The current density is equal:
J=I/A where A is the area of the wire.
J=4A/(π*1*10^-6m^2)=1.27 *10^6 A/m^2
The resistence of the wire is given by:
R=L/(σ*A) where σ and L are the conductivity and the length of the wire, respectively.
Then we have:
σ= L/(R*A)=1/(5.5*10^-3*π*1*10^-6)=57.9 *10^6 Ω*m
The drift velocity of free electrons is given by:
Vd=i/(n*A*e) where n is the numer of electrons per volume. e is the electron charge.
then we have:
Vd=J/(n*e)= 1.27 *10^6/(8.43*10^28*1.6*10^-19)=94.16 *10^-6 m/s
Finally, the mobility of free electrons is equal to:
μ=Vd/E ; E=J/σ
μ=E*σ/J= 94.16*10^-6*57.9 *10^6/1.27 *10^6=4.29*10^-3 m^2/V*s
Answer:
B. the acceleration of a skydiver depends upon the force of gravity and wind resistance
Explanation:
Newtons second law of motion states that: the force (F) acting upon an object is directly proportional to the mass (M) of the object and the acceleration (a).
Basically this law states that the acceleration of a body is dependent on the force and mass of the body. If the force exerted on the body changes the acceleration will also change. and if the mass of the body changes, the acceleration will also be affected
from the options, the only option that refers to acceleration is option B
Has mass and occupied space
Answer:
1.17 m
Explanation:
From the question,
s₁ = vt₁/2................ Equation 1
Where s₁ = distance of the reflecting object for the first echo, v = speed of the sound in air, t₁ = time to dectect the first echo.
Given: v = 343 m/s, t = 0.0115 s
Substitute into equation 1
s₁ = (343×0.0115)/2
s₁ = 1.97 m.
Similarly,
s₂ = vt₂/2.................. Equation 2
Where s₂ = distance of the reflecting object for the second echo, t₂ = Time taken to detect the second echo
Given: v = 343 m/s, t₂ = 0.0183 s
Substitute into equation 2
s₂ = (343×0.0183)/2
s₂ = 3.14 m
The distance moved by the reflecting object from s₁ to s₂ = s₂-s₁
s₂-s₁ = (3.14-1.97) m = 1.17 m
