1. If a train of freight cars, each 10 m long, rolls by you at the rate of three cars each second, what is the speed of the train?

Question

2. A water wave oscillates up and down three times each second and the distance between wave crests is 2 m.

a. What is its frequency?

b. What is its wavelength?

c. What is its wave speed?

3. The sound from a 60-Hz razor spreads out at 340 meters per second.

a. What is the frequency of the sound waves?

b. What is their period?

c. What is their speed?

d. What is their wavelength?

Accepted Answer

1. 30 m/s. We can see this in two ways. According to the definition of speed,

[latex]v=\frac{d}{t}=\frac{3 imes 10 m }{1 s }=30 m / s[/latex],

since 30 m of train passes you in 1 s. If we compare our train to wave motion, where wavelength corresponds to 10 m and frequency is 3 Hz, then

[latex]Speed=frequency imes wavelength =3 Hz imes 10 m =30 m/s[/latex]

2. a. 3 Hz

b. 2 m

c. [latex]\begin{aligned} ext { Wave speed } &= ext {frequency } imes ext { wavelength } \&=3 / s imes 2 m =6 m / s\end{aligned}[/latex]

3. a. 60 Hz

b. 1/60 second

c. 340 m/s

d.5.7 m.

Question 12.S&C.2: 1. If a train of freight cars, each 10 m long, rolls by you ...