Answer:
a) h = 0.1:
, h = 0.01:
, h = 0.001:
, b) The instantaneous velocity of the ball when
is
feet per second.
Step-by-step explanation:
a) We know that
describes the position of the ball, measured in feet, in time, measured in seconds, and the average velocity (
), measured in feet per second, can be done by means of the following definition:
![\bar v = \frac{y(2+h)-y(2)}{h}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20%5Cfrac%7By%282%2Bh%29-y%282%29%7D%7Bh%7D)
Where:
- Position of the ball evaluated at
, measured in feet.
- Position of the ball evaluated at
, measured in feet.
- Change interval, measured in seconds.
Now, we obtained different average velocities by means of different change intervals:
![h = 0.1\,s](https://tex.z-dn.net/?f=h%20%3D%200.1%5C%2Cs)
![y(2) = 30\cdot (2) - 10\cdot (2)^{2}](https://tex.z-dn.net/?f=y%282%29%20%3D%2030%5Ccdot%20%282%29%20-%2010%5Ccdot%20%282%29%5E%7B2%7D)
![y (2) = 20\,ft](https://tex.z-dn.net/?f=y%20%282%29%20%3D%2020%5C%2Cft)
![y(2.1) = 30\cdot (2.1)-10\cdot (2.1)^{2}](https://tex.z-dn.net/?f=y%282.1%29%20%3D%2030%5Ccdot%20%282.1%29-10%5Ccdot%20%282.1%29%5E%7B2%7D)
![y(2.1) = 18.9\,ft](https://tex.z-dn.net/?f=y%282.1%29%20%3D%2018.9%5C%2Cft)
![\bar v = \frac{18.9\,ft-20\,ft}{0.1\,s}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20%5Cfrac%7B18.9%5C%2Cft-20%5C%2Cft%7D%7B0.1%5C%2Cs%7D)
![\bar v = -11\,\frac{ft}{s}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20-11%5C%2C%5Cfrac%7Bft%7D%7Bs%7D)
![h = 0.01\,s](https://tex.z-dn.net/?f=h%20%3D%200.01%5C%2Cs)
![y(2) = 30\cdot (2) - 10\cdot (2)^{2}](https://tex.z-dn.net/?f=y%282%29%20%3D%2030%5Ccdot%20%282%29%20-%2010%5Ccdot%20%282%29%5E%7B2%7D)
![y (2) = 20\,ft](https://tex.z-dn.net/?f=y%20%282%29%20%3D%2020%5C%2Cft)
![y(2.01) = 30\cdot (2.01)-10\cdot (2.01)^{2}](https://tex.z-dn.net/?f=y%282.01%29%20%3D%2030%5Ccdot%20%282.01%29-10%5Ccdot%20%282.01%29%5E%7B2%7D)
![y(2.01) = 19.899\,ft](https://tex.z-dn.net/?f=y%282.01%29%20%3D%2019.899%5C%2Cft)
![\bar v = \frac{19.899\,ft-20\,ft}{0.01\,s}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20%5Cfrac%7B19.899%5C%2Cft-20%5C%2Cft%7D%7B0.01%5C%2Cs%7D)
![\bar v = -10.1\,\frac{ft}{s}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20-10.1%5C%2C%5Cfrac%7Bft%7D%7Bs%7D)
![h = 0.001\,s](https://tex.z-dn.net/?f=h%20%3D%200.001%5C%2Cs)
![y(2) = 30\cdot (2) - 10\cdot (2)^{2}](https://tex.z-dn.net/?f=y%282%29%20%3D%2030%5Ccdot%20%282%29%20-%2010%5Ccdot%20%282%29%5E%7B2%7D)
![y (2) = 20\,ft](https://tex.z-dn.net/?f=y%20%282%29%20%3D%2020%5C%2Cft)
![y(2.001) = 30\cdot (2.001)-10\cdot (2.001)^{2}](https://tex.z-dn.net/?f=y%282.001%29%20%3D%2030%5Ccdot%20%282.001%29-10%5Ccdot%20%282.001%29%5E%7B2%7D)
![y(2.001) = 19.99\,ft](https://tex.z-dn.net/?f=y%282.001%29%20%3D%2019.99%5C%2Cft)
![\bar v = \frac{19.99\,ft-20\,ft}{0.001\,s}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20%5Cfrac%7B19.99%5C%2Cft-20%5C%2Cft%7D%7B0.001%5C%2Cs%7D)
![\bar v = -10\,\frac{ft}{s}](https://tex.z-dn.net/?f=%5Cbar%20v%20%3D%20-10%5C%2C%5Cfrac%7Bft%7D%7Bs%7D)
b) The instantaneous velocity when
can be obtained by using the following limit:
![v(t) = \lim_{h \to 0} \frac{x(t+h)-x(t)}{h}](https://tex.z-dn.net/?f=v%28t%29%20%3D%20%5Clim_%7Bh%20%5Cto%200%7D%20%5Cfrac%7Bx%28t%2Bh%29-x%28t%29%7D%7Bh%7D)
![v(t) = \lim_{h \to 0} \frac{30\cdot (t+h)-10\cdot (t+h)^{2}-30\cdot t +10\cdot t^{2}}{h}](https://tex.z-dn.net/?f=v%28t%29%20%3D%20%20%5Clim_%7Bh%20%5Cto%200%7D%20%5Cfrac%7B30%5Ccdot%20%28t%2Bh%29-10%5Ccdot%20%28t%2Bh%29%5E%7B2%7D-30%5Ccdot%20t%20%2B10%5Ccdot%20t%5E%7B2%7D%7D%7Bh%7D)
![v(t) = \lim_{h \to 0} \frac{30\cdot t +30\cdot h -10\cdot (t^{2}+2\cdot t\cdot h +h^{2})-30\cdot t +10\cdot t^{2}}{h}](https://tex.z-dn.net/?f=v%28t%29%20%3D%20%20%5Clim_%7Bh%20%5Cto%200%7D%20%5Cfrac%7B30%5Ccdot%20t%20%2B30%5Ccdot%20h%20-10%5Ccdot%20%28t%5E%7B2%7D%2B2%5Ccdot%20t%5Ccdot%20h%20%2Bh%5E%7B2%7D%29-30%5Ccdot%20t%20%2B10%5Ccdot%20t%5E%7B2%7D%7D%7Bh%7D)
![v(t) = \lim_{h \to 0} \frac{30\cdot t +30\cdot h-10\cdot t^{2}-20\cdot t \cdot h-10\cdot h^{2}-30\cdot t +10\cdot t^{2}}{h}](https://tex.z-dn.net/?f=v%28t%29%20%3D%20%20%5Clim_%7Bh%20%5Cto%200%7D%20%5Cfrac%7B30%5Ccdot%20t%20%2B30%5Ccdot%20h-10%5Ccdot%20t%5E%7B2%7D-20%5Ccdot%20t%20%5Ccdot%20h-10%5Ccdot%20h%5E%7B2%7D-30%5Ccdot%20t%20%2B10%5Ccdot%20t%5E%7B2%7D%7D%7Bh%7D)
![v(t) = \lim_{h \to 0} \frac{30\cdot h-20\cdot t\cdot h-10\cdot h^{2}}{h}](https://tex.z-dn.net/?f=v%28t%29%20%3D%20%20%5Clim_%7Bh%20%5Cto%200%7D%20%5Cfrac%7B30%5Ccdot%20h-20%5Ccdot%20t%5Ccdot%20h-10%5Ccdot%20h%5E%7B2%7D%7D%7Bh%7D)
![v(t) = \lim_{h \to 0} 30-20\cdot t-10\cdot h](https://tex.z-dn.net/?f=v%28t%29%20%3D%20%20%5Clim_%7Bh%20%5Cto%200%7D%2030-20%5Ccdot%20t-10%5Ccdot%20h)
![v(t) = 30\cdot \lim_{h \to 0} 1 - 20\cdot t \cdot \lim_{h \to 0} 1 - 10\cdot \lim_{h \to 0} h](https://tex.z-dn.net/?f=v%28t%29%20%3D%2030%5Ccdot%20%20%5Clim_%7Bh%20%5Cto%200%7D%201%20-%2020%5Ccdot%20t%20%5Ccdot%20%20%5Clim_%7Bh%20%5Cto%200%7D%201%20-%2010%5Ccdot%20%20%5Clim_%7Bh%20%5Cto%200%7D%20h)
![v(t) = 30-20\cdot t](https://tex.z-dn.net/?f=v%28t%29%20%3D%2030-20%5Ccdot%20t)
And we finally evaluate the instantaneous velocity at
:
![v(2) = 30-20\cdot (2)](https://tex.z-dn.net/?f=v%282%29%20%3D%2030-20%5Ccdot%20%282%29)
![v(2) = -10\,\frac{ft}{s}](https://tex.z-dn.net/?f=v%282%29%20%3D%20-10%5C%2C%5Cfrac%7Bft%7D%7Bs%7D)
The instantaneous velocity of the ball when
is
feet per second.