question_answer

A 2000 kg car travelling at 72 km/h runs into a concrete wall and stops in 0.05s. What magnitude of impulse did the wall exert on the car?

Answer:

\[m=2000\,\,kg\] \[v=72km/h=72\times \frac{5}{18}m/s=20m/s\] \[t=0.05s,\,\,impulse=?\] \[a=\frac{v}{t}=\frac{20}{0.05}m/{{s}^{2}}=400m/{{s}^{2}}\] \[F=ma=2000\times 400=800000N\] \[\therefore \,\,\operatorname{Im}pulse=F\times t=800000\times 0.5s\] \[=40000\,\,Ns=4\times {{10}^{4}}Ns\] \[\therefore \]Magnitude of impulse did the wall exert on the car \[=4\times {{10}^{4}}Ns.\]