Question Number 181052 by Acem last updated on 20/Nov/22
Commented by Acem last updated on 20/Nov/22
$$\ast\:{When}\:{the}\:{car}\:{is}\:\mathrm{6}\:{Km}\:{from}\:{A} \\ $$
Commented by mr W last updated on 22/Nov/22
$$\frac{\mathrm{220}}{\:\sqrt{\mathrm{7}}}\:{km}/{h} \\ $$$${what}'{s}\:{your}\:{solution}? \\ $$
Commented by Acem last updated on 22/Nov/22
$${The}\:{same}\:{result}\:\left(:\right. \\ $$$${let}'{s}\:{write}\:{our}\:{methods} \\ $$
Answered by Acem last updated on 22/Nov/22
Answered by mr W last updated on 23/Nov/22
Commented by mr W last updated on 23/Nov/22
$${L}=\sqrt{\mathrm{9}^{\mathrm{2}} +\mathrm{18}^{\mathrm{2}} +\mathrm{9}×\mathrm{18}}=\mathrm{9}\sqrt{\mathrm{7}} \\ $$$$\mathrm{cos}\:\theta=\frac{\mathrm{9}^{\mathrm{2}} +\left(\mathrm{9}\sqrt{\mathrm{7}}\right)^{\mathrm{2}} −\mathrm{18}^{\mathrm{2}} }{\mathrm{2}×\mathrm{9}×\mathrm{9}\sqrt{\mathrm{7}}}=\frac{\mathrm{2}}{\:\sqrt{\mathrm{7}}} \\ $$$${since}\:“{I}''\:{don}'{t}\:{move},\:{how}\:{fast}\:{the} \\ $$$${distance}\:{from}\:{the}\:{car}\:{to}\:{me}\:{changes} \\ $$$${means}\:{how}\:{fast}\:{the}\:{car}\:{moves}\: \\ $$$${towards}\:{me}\:{at}\:{that}\:{moment},\:\:{that}'{s}\: \\ $$$${the}\:{component}\:{of}\:{its}\:{velocity}\:{in}\:{my}\: \\ $$$${direction},\:{i}.{e}. \\ $$$${v}\:\mathrm{cos}\:\theta=\frac{\mathrm{2}{v}}{\:\sqrt{\mathrm{7}}}=\frac{\mathrm{220}}{\:\sqrt{\mathrm{7}}}\:{km}/{h}. \\ $$
Commented by mr W last updated on 23/Nov/22
$${if}\:“{I}''\:{also}\:{move}\:{with}\:{speed}\:{v}_{\mathrm{1}} ,\:{then} \\ $$$${it}\:{is}\:{v}\:\mathrm{cos}\:\theta+{v}_{\mathrm{1}} \:\mathrm{cos}\:\theta_{\mathrm{1}} . \\ $$
Commented by mr W last updated on 23/Nov/22
