Answer:
2.62seconds
Explanation:
Speed is defined as the ratio of the distance covered by a body with respect to time.
Speed v = Distance (s)/Time (t)
For a traveling sound wave, the distance between the source of a sound and the reflector is '2S'.
Speed v = 2 × distance (S)/Time (T)
V = 2S/t
2S = vt
Given speed of the wave = 342m/s
Distance covered = 450m
t = 2S/v
t = (2×450)/343
t = 900/343
t = 2.62seconds
It will take him 2.62seconds for him to hear his own voice echo off of the wall.
Answer:
1) The maximum jump height is reached at A. 
2) The maximum center of mass height off of the ground is B. 
3) The time of flight is C. 
4) The distance of jump is B. 
Explanation:
First of all we need to decompose velocity in its rectangular components, so
1) We use, 
, as we clear it for 
and using the fact that 
at max height, we obtain 
2) We can use the formula 
for 
, so
3) We can use the formula 
, to find total time of fligth, so 
, as it is a second-grade polynomial, we find that its positive root is 
4) Finally, we use 
, as it has an additional displacement of 
due the leg extension we obtain,
, aprox 
Answer:
Hello todays answer should be False i am sorry if i am incorrect-Lucy
Explanation:
Answer: B. Concrete
Explanation:
Let N = reacting force pressing the bodies in context together (units in Newtons),
The question stated that the force pressing the two mounted/stacked objects together is equal to the weight of the object on top.
We need to start by finding the weight of the piece of wood.
friction is given by
f = μN
The value of f is 22.5,
and from the chart reference the coefficient of friction between wood and stone, μ is 0.30.
22.5 = 75. 0.30
Putting the values into the equation: 22.5 = 0.30N.
Divide both sides by 0.30 to find the value of N:
N= 22.5/0.3 = 75
Now that the piece of wood will be placed on another surface, its weight of 75 Newton is the force pressing the two bodies together.
To determine the new surface, you should find the new coefficient of friction by using the new value of the force of friction given 46.5:
46.5 = µ(75).
Divide both sides by 75 to isolate μ.
The refer chart also indicates that the coefficient of friction equals 0.62 between wood and concrete, so the new surface corresponding to 0.62 is the concrete, which is (B).
- Static friction: when an object is not moving
- Kinetic friction: if an object is moving
- Rolling friction: when there is rolling (wheel,..)
