Answer:
e) 120m/s
Explanation:
When the ball reaches its highest point, its velocity becomes zero, meaning
.
where is the initial velocity.
Solving for we get
which is the time it takes the ball to reach the highest point.
Now, after the ball has reached its highest point, it turns around and falls downwards. After time since it had reached the highest point, the ball has traveled downwards and the velocity it has gained is
,
and we are told that this is twice the initial velocity ; therefore,
which gives
Thus, the total time taken to reach velocity is
This , we are told, is 36 seconds; therefore,
and solving for we get:
which from the options given is choice e.
The correct options are:
1 How tall are you?
2How far is it from your house to your school?
3How wide is your refrigerator?
All these measurements involve to measure a length. Instead, the other two options involve to measure different physical quantities; for instance, the question
4 How much does your sister weigh?
Involve to measure a weight (and so, a mass), while the question
5 How warm is it in San Diego?
requires to measure a temperature.
The concept required to solve this problem is related to the wavelength.
The wavelength can be defined as the distance between two positive crests of a wave.
The waves are in phase, then the first distance is
And out of the phase when
Thus the wavelength is
Here,
Wavelength
If we rearrange the equation to find it, we will have
Therefore the wavelength of the sound is 20cm.