What Speed is the Racecar Moving?

  • Thread starter Thread starter dmolson
  • Start date Start date
  • Tags Tags
    Sound
AI Thread Summary
The discussion centers on calculating the speed of a racecar based on the change in pitch of its engine sound as it passes spectators. The sound frequency drops to 0.75 times its original value, indicating a specific speed related to the Doppler effect. Participants are encouraged to share relevant formulas and methods to solve the problem. Options for the racecar's speed include 68 m/s, 49 m/s, 61 m/s, and 72 m/s. The thread seeks assistance in understanding the calculations involved in determining the racecar's speed.
dmolson
Messages
19
Reaction score
0
The pitch of the sound from a racecar engine drops the musical interval of a fourth when it passes the spectators. This means the frequency of the sound after passing is 0.75 times what it was before. How fast is the racecar moving?

a. 68 m/s
b. 49 m/s
c. 61 m/s
d. 72 m/s
 
Physics news on Phys.org
I cannot figure out how to work this problem out, any help would be great. Thanks in advance.
 
Think of what formulae that comes to your mind when you do this question.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

How Fast is the Racecar Moving Based on the Doppler Effect?
Replies
1
Views
7K
Audio interference of sound waves from two speakers
Replies
19
Views
4K
Sound Interference Problem -- Observer moving between two speakers
Replies
3
Views
4K
Doppler effect train frequency question
Replies
4
Views
2K
Doppler effect (source and detector moving together)
Replies
4
Views
2K
What is the wavelength of a sound wave?
Replies
4
Views
2K
Kinematics/speed of sound question
Replies
3
Views
3K
Stress, Strain, and Sound in a Projectile Steel Rod
Replies
2
Views
2K
How Is the Distance to the Seabed Calculated Using Sonar?
Replies
4
Views
3K
Sound Waves in Different Mediums
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top