A wave on a long elastic string is described by

PHYSICS · Subjective · A Level · Physics · Waves · Waves

Problem

y = A\sin(kx \pm \omega t)

. At

t = 0

, a crest is at

x = 0.15\,\text{m}

. After

0.20\,\text{s}

the same crest is at

x = 0.75\,\text{m}

. Given

k = 8\pi\,\text{rad m}^{-1}

, determine: (a) the correct sign (plus or minus) before the

\omega t

term, (b) the speed of the wave.