I didn’t know water has calories
Answer:
10m
Explanation:
The object distance and image distance is the same from the mirror. so the image is 5m behind the mirror.
5+5=10
Answer:
10.2 Watt
Explanation:
= number of turns in flat coil = 160
= area = 0.20 m²
B₀= initial magnetic field = 0.40 T
= final magnetic field = - 0.40 T
Change in magnetic field is given as
ΔB = B - B₀ = - 0.40 - 0.40 = - 0.80 T
= time taken for the magnetic field to change = 2.0 s
Induced emf is given as
= 12.8 volts
= Resistance of the coil = 16 Ω
Power is given as
= 10.2 Watt
Angry sound level = 70 db
Soothing sound level = 50 db
Frequency, f = 500 Hz
Assuming speed of sound = 345 m/s
Density (assumed) = 1.21 kg/m^3
Reference sound intensity, Io = 1*10^-12 w/m^2
Part (a): Initial sound intensity (angry sound)
10log (I/Io) = Sound level
Therefore,
For Ia = 70 db
Ia/(1*10^-12) = 10^(70/10)
Ia = 10^(70/10)*10^-12 = 1*10^-5 W/m^2
Part (b): Final sound intensity (soothing sound)
Is = 50 db
Therefore,
Is = 10^(50/10)*10^-12 = 18*10^-7 W/m^2
Part (c): Initial sound wave amplitude
Now,
I (W/m^2) = 0.5*A^2*density*velocity*4*π^2*frequency^2
Making A the subject;
A = Sqrt [I/(0.5*density*velocity*4π^2*frequency^2)]
Substituting;
A_initial = Sqrt [(1*10^-5)/(0.5*1.21*345*4π^2*500^2)] = 6.97*10^-8 m = 69.7 nm
Part (d): Final sound wave amplitude
A_final = Sqrt [(1*10^-7)/(0.5*1.21*345*4π^2*500^2)] = 6.97*10^-9 m = 6.97 nm
Answer: D
Explanation: The chemical bonds in the food store energy that is released when we eat it.
