Question

If a car can go from 0 to 60 mi/hr in 8.0 seconds, what would be its final speed after 5.0 seconds if its starting speed were 50 mi/hr?

Answer 1

`v_1=60\ (mi)/(h)\\\\t_1=8.0\ s=(8)/(3600)\ h=(1)/(450)\ h\\--------------\\a=(v)/(t)\\\\a=(60)/((1)/(450))\ (mi)/(h^2)=27000\ (mi)/(h^2)\\--------------\\v_o=50\ (mi)/(h)\\\\t=5.0\ s=(5)/(3600)\ h=(1)/(720)\ h\\--------------`


`v=v_o+at\\\\\\v=50\ (mi)/(h)+27000\ (mi)/(h^2)\cdot(1)/(720)\ h=50\ (mi)/(h)+37.5\ (mi)/(h)=87.5\ (mi)/(h)\leftarrow Answer`

Answer 2

`a= (V)/(t) \ \ \ \Rightarrow\ \ a= (60\ [mi/hr])/(8\ [s]) \\ \\the\ final\ speed\ after\ 5.0\ seconds\\ \\V=50\ [mi/hr]+5\ [s]\ \cdot (60\ [mi/hr])/(8\ [s])=50\ [mi/hr] + (5)/(8) \cdot 60\ [mi/hr]=\\ \\=50\ [mi/hr]+37.5\ [mi/hr]=87.5\ [mi/hr]`