Final answer:
The length of a string can be determined by the String method length(). To calculate the speed of a wave on a string, measurements of the distance between posts, amplitude of the wave, and the tension in the string are needed.
Step-by-step explanation:
The length of a string can be determined by a. the String method length(). This is a method provided by the String class in many programming languages, such as Java, to get the number of characters in a string. Options b. the String instance variable length and c. the String method strlen() are incorrect because in many programming languages, strings do not have a variable called length as an instance variable, and strlen() is often associated with programming in C, not a method of the String class.
To determine the speed of a wave on a string, students need to take additional measurements beyond the time for the wave to oscillate. The correct answer is e. The distance between the two posts, the amplitude of the wave, and the tension in the string. This information is necessary because the speed of the wave on a string is determined by the formula v = √(T/μ), where v is the speed of the wave, T is the tension in the string, and μ (mu) is the linear mass density of the string. The distance between the posts and the amplitude of the wave can help provide context for additional calculations and understanding of the wave properties.