Answer:
Explanation:
Intensity of sound = sound energy emitted by source / 4 π d² , where d is distance of the source .
A )
Intensity of sound at 1 m distance = 60 /4 π d²
d = 1 m
Intensity of sound at 1 m distance = 60 /(4 π 1²)
= 4.78 W m⁻² s⁻¹
B )
Intensity of sound at 1.5 m distance = 60 /4 π d²
d = 1.5 m
Intensity of sound at 1 m distance = 60 /(4 π 1.5²)
= 2.12 W m⁻² s⁻¹
C )
Intensity of sound due to 4 speakers at 1.5 m distance = 4 x 60 /4 π d²
d = 1.5 m
= 4 x 60 /(4 π 1.5²)
= 8.48 W m⁻² s⁻¹
D )
Intensity of sound due to .06 W speaker must be 10⁻¹² W s ⁻² . Let the distance be d .
.06 /4 π d² = 10⁻¹²
d² = .06 /4 π 10⁻¹²
d = 6.9 x 10⁴ m .
Answer:
i think its c and d
(btw thats my best guess)
Explanation:
Answer:
7. (D) uniformly accelerated vertical motion
8. (A) zero
9. (A) zero
10. (C) parabolic
Answer:
21.42m/S
Explanation:
Hello!
To solve this problem we must perform the following steps.
1. Find the distance traveled from until the driver reacts, this is achieved using the equation for constant speed movement.
X1=VT
where
x= distance traveled
v=initial speed
T=time=0.75s
X1=0.75Vo
we must take into account that the total distance is the sum of the distance at which the pilot reacts (x1) and when it starts to decelerate (x2)
39=0.75Vo+X2
X2=39-0.75Vo
2. Now we use the equation that defines a movement with constant acceleration.

where
Vf = final speed=0m/s
Vo = Initial speed
A = acceleration
=-10m/s2
X2 = displacement
now we use the ecuation of step 1

solving

Now we solve the quadratic equation and find the value of Vo
the solutions are 21.42m/S, -36.41m/S
as the speed must be positive we conclude that the answer is 21.42m/S