Answer:
Explanation:
We apply Newton's second law at the crate :
∑F = m*a (Formula 1)
∑F : algebraic sum of the forces in Newton (N)
m : mass in kilograms (kg)
a : acceleration in meters over second square (m/s²)
Data:
m=90kg : crate mass
F= 282 N
μk =0.351 :coefficient of kinetic friction
g = 9.8 m/s² : acceleration due to gravity
Crate weight (W)
W= m*g
W= 90kg*9.8 m/s²
W= 882 N
Friction force : Ff
Ff= μk*N Formula (2)
μk: coefficient of kinetic friction
N : Normal force (N)
Problem development
We apply the formula (1)
∑Fy = m*ay , ay=0
N-W = 0
N = W
N = 882 N
We replace the data in the formula (2)
Ff= μk*N = 0.351* 882 N
Ff= 309.58 N
We apply the formula (1) in x direction:
∑Fx = m*ax , ax=0
282 N - 309.58 N = 90*a
a= (282 N - 309.58 N ) / (90)
a= - 0.306 m/s²
Kinematics of the crate
Because the crate moves with uniformly accelerated movement we apply the following formula :
vf²=v₀²+2*a*d Formula (3)
Where:
d:displacement in meters (m)
v₀: initial speed in m/s
vf: final speed in m/s
a: acceleration in m/s²
Data
v₀ = 0.850 m/s
d = 0.75 m
a= - 0.306 m/s²
We replace the data in the formula (3)
vf²=(0.850)²+(2)( - 0.306 )(0.75 )
C. Elastic collision. A perfect elastic collision is on that doesn't result in any k.e loss during the collision.
1) am radio waves
The lowest and highest frequencies of the radio signals are:
The speed of the waves is the speed of light,
, so to find the corresponding wavelengths we can use the basic relationship between frequency, wavelength and speed of a wave:
where f is the frequency and
the wavelength.
The wavelength corresponding to the lowest frequency is:
while the wavelength corresponding to the highest frequency is
So, the range of wavelengths is [187.5-545] m.
2) fm radio waves
This time, the lowest and highest frequencies of the radio waves are:
So the corresponding wavelengths are:
Therefore, the range of wavelengths of the rm radio signals is [2.8-3.4] m.
Answer:
The most important is that the thermal conductivity of the armadillas several orders of magnitude lower than the thermal conductivity of the metal, therefore it is easier to maintain the temperature in winter
Explanation:
Cement and bricks are used in the construction of houses instead of metal, for several reasons
* The most important is that the thermal conductivity of the armadillas several orders of magnitude lower than the thermal conductivity of the metal, therefore it is easier to maintain the temperature in winter
* Metal has more oxidation problems than brick
* The cost of sheet metal is higher than the cost of cement brick.
Answer:
D. Community members, teachers
Explanation:
The Highscope curriculum encourages community members to have a very active role in the learning of each child, helping in their development. The activities are child-initiated and guided by parents and community members in general, having a role of partners, contrary to the role that they traditionally had as supervisors.