Answer:
minimum length of a surface crack is 18.3 mm
Explanation:
Given data
plane strain fracture toughness K = 82.4 MPa m1/2
stress σ = 345 MPa
Y = 1
to find out
the minimum length of a surface crack
solution
we will calculate length by this formula
length = 1/π ( K / σ Y)²
put all value
length = 1/π ( K / σ Y)²
length = 1/π ( 82.4
/ 345× 1)²
length = 18.3 mm
minimum length of a surface crack is 18.3 mm
The expression of the electric flux is

Here,
Q = Total charge enclosed in the closed surface
= Permittivity due to free space
Rearranging to find the charge,

Replacing with our values we have finally



The charge enclosed by the box is 0.1684nC
The sign of the charge can be decided by using the direction of the flux. The charge enclosed by the cube can be calculated by using the electric flux and the permitivity of free space.
Answer:
a) 107.1875 Hz
b) 214.375 Hz
c) 321.5625 Hz
Explanation:
L = length of the open organ pipe = 1.6 m
v = speed of sound = 343 m/s
f = fundamental frequency
fundamental frequency is given as

inserting the values


Hz
b)
first overtone is given as
f' = 2f
f' = 2 (107.1875)
f' = 214.375 Hz
c)
first overtone is given as
f'' = 3f
f'' = 3 (107.1875)
f'' = 321.5625 Hz
If the resistance of the Air is ignored, we can use the theory given by Galileo in which he warned that the thermal velocity of a body in free fall was given by

Where
g = Gravitational acceleration
t = time
As we can see the speed of objects in free fall is indifferent to the position that is launched (as long as the resistance of the air is ignored) or its mass.
Both bodies will end with the same thermal speed.