Question Number 29360 by NECx last updated on 08/Feb/18
$${Two}\:{stones}\:{are}\:{thrown}\:{up}\: \\ $$$${simultaneously}\:{from}\:{the}\:{edge}\:{of} \\ $$$${a}\:{cliff}\:\mathrm{200}{m}\:{high}\:{with}\:{initial} \\ $$$${speeds}\:{of}\:\mathrm{15}{ms}^{−\mathrm{1}} \:{and}\:\mathrm{30}{ms}^{−\mathrm{1}} . \\ $$$${Verify}\:{that}\:{the}\:{graph}\:{shown} \\ $$$${below}\:{correctly}\:{represents}\:{the} \\ $$$${time}\:{variation}\:{of}\:{the}\:{relative} \\ $$$${position}\:{of}\:{the}\:{second}\:{stone} \\ $$$${with}\:{respect}\:{to}\:{the}\:{first}.{Neglect} \\ $$$${air}\:{resistance}\:{and}\:{assume}\:{that} \\ $$$${the}\:{stones}\:{do}\:{not}\:{rebound}.{Take} \\ $$$${g}=\mathrm{10}{m}/{s}^{\mathrm{2}} .\:{Give}\:{the}\:{equations}\:{of} \\ $$$${the}\:{linear}\:{and}\:{curved}\:{parts}\:{of} \\ $$$${the}\:{plot}. \\ $$
Commented by NECx last updated on 08/Feb/18
Answered by 33 last updated on 08/Feb/18
$$ \\ $$$$ \\ $$$${v}_{{rel}} \:=\:\mathrm{30}\:−\:\mathrm{15}\:=\:\mathrm{15}\:{m}/{s}\:\:\:...{i} \\ $$$$\left(\:{taking}\:{upward}\:{direction}\:{to}\:{be}\:\right. \\ $$$$\left.{positive}\:\right) \\ $$$${a}_{{rel}\:} =\:\mathrm{10}\:−\:\mathrm{10}\:=\:\mathrm{0}\:{m}/{s}^{\mathrm{2}} \\ $$$${eq}\:\:\:...{i}\:{represents}\:{straight}\:{line} \\ $$$$ \\ $$$${as}\:{one}\:{of}\:{the}\:{stones}\:{hit}\:\left(\mathrm{15}\:{m}/{s}\right) \\ $$$${v}_{{rel}} \:>\:\mathrm{30}\:{m}/{s} \\ $$$${a}_{{rwl}} \:=\:\mathrm{0}\:−\:\mathrm{10}\:=\:−\mathrm{10}{m}/{s}^{\mathrm{2}} \\ $$$$\Rightarrow{curved}\:{graph}\:{starts}\:{as}\:{the}\:\mathrm{15}{m}/{s} \\ $$$${stone}\:{hits}\:{the}\:{ground} \\ $$$$ \\ $$
Commented by NECx last updated on 08/Feb/18
$${according}\:{to}\:{the}\:{text}\:{book}\:{this}\:{is} \\ $$$${wrong}\:{sir}. \\ $$
Commented by 33 last updated on 08/Feb/18
$${plz}\:{tell}\:{me}\:{whats}\:{the}\:{problem} \\ $$$${in}\:{this}\:{one}. \\ $$
Answered by Tinkutara last updated on 08/Feb/18
Commented by Tinkutara last updated on 08/Feb/18
First image http://ibb.co/mArn1H