2. 2
The speed of a wave on a string
• When a portion of a string under tension is displaced, a wave will be
launched along the string.
• It is probably not surprising that the velocity will depend on the
tension force F and on the weight of the string (actually the
mass/unit length µ). Think of a guitar whose strings are all at the
same tension. The thicker strings will produce a lower tone due to
the slower speed of the wave (we will discuss standing waves
shortly).
• Here is the expression for the propagation speed:
3. 3
• Example : Two children are playing with a string that is fixed at
one end. By moving their hand up and down they can generate a
wave pulse. They want to take a picture of it, but it's too fast. How
can they make the pulse move slower?
• (choose ALL that apply)
• They could move their hands up and down a larger distance as they
generate the pulse.
• They could loosen the string tension.
• They could tighten the string tension.
• They could move their hand up and down slower.
• They could use a heavier string.
• They could use a lighter string.