Insulating materials are rated by their _____. specific heat heat index r-value temperature resistance
2 answers:
Answer: Option (c) is the correct answer.
Explanation:
The difference in temperature when per unit of heat flux is required by one unit of heat flux between a barrier of warmer and colder surface present in steady state condition is known as R-value.
Mathematically, R-value =
Thermal resistance of insulating products or materials can be known with the help of R-value. As more is the r-value of a substance more will be its insulating power.
Therefore, we can conclude that insulating materials are rated by their r-value.
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Answer:
37.42 m/s
Explanation:
We know that apparent frequency, is given by
where f is the given frequency in this case 392, V is the speed of sound in air which is given as 343 and
is the speed of car which is unknown, \bar f is given as 440 Hz
a) 2.75 s
The vertical position of the ball at time t is given by the equation
where
h = 4 m is the initial height of the ball
u = 12 m/s is the initial velocity of the ball (upward)
g = 9.8 m/s^2 is the acceleration of gravity (downward)
We can find the time t at which the ball reaches the ground by substituting y=0 into the equation:
This is a second-order equation. By solving it for t, we find:
t = -0.30 s
t = 2.75 s
The first solution is negative, so we discard it; the second solution, t = 2.75 s, is the one we are looking for.
b) -15.0 m/s (downward)
The final velocity of the ball can be calculated by using the equation:
where
u = 12 m/s is the initial (upward) velocity
g = 9.8 m/s^2 is the acceleration of gravity (downward)
t is the time
By subsisuting t = 2.75 s, we find the velocity of the ball as it reaches the ground:
And the negative sign means the direction is downward.