Answer:
15km/h
Explanation:
Time taken to complete 30km/h=2 hours=15km/h hence the average speed is 15km/h.
The three strata of study within the study of kinesiology are:
1. Core scientific domain: the core scientific domain deals with the sub disciplines that are found in kinesiology. Examples of these sub disciplines are biomechanics, sport medicine, exercise physiology, history of sport and dance, neurophysiology of performance, physiology of sport, sociology of sport, etc.
2. Sociocultural based form of movement: this aspect of kinesiology deals with the different types of games, sport and dance that are practised in different cultures and countries. The aspect studies expert skills that are involved in different sociocultural based movements. Examples of sociocultural based movements are aquatics, combative, individual sport, running, etc.
3. Methods in professional application: these deals with the professional training and careers that are available in kinesiology. There are generally five areas of professional training, they are: capacity building, management and administration, performance enhancement, instruction in physical education and research.
The frequency, the speed and the wavelength of a wave are related by the following equation:

(1)
where
f is the frequency

is the wavelength
v is the wave speed
The speed of the wave does depend only on the properties of the medium, so since the wave is still traveling in air, the medium has not changed and therefore the speed remains the same. We see instead from eq.(1) that the frequency is inversely proportional to the wavelength, so if the wavelength is decreased by half, we see that the frequency will double.