## anonymous one year ago A car moving with a speed of 108 km/h is brought to rest in a distance of 60 m. The car's acceleration is -7.5 m/s/s. How much time did the car take to stop?

1. Michele_Laino

the stopping work is given by the kinetic energy of the car, so if I call with $$F$$ the stopping force, and with $$d$$ the space traveled by the car, then we can write: $Fd = \frac{1}{2}m{v^2}$ now, we have that $$F=ma$$ where $$a$$ is the deceleration, so we can write: $mad = \frac{1}{2}m{v^2}$ and finally: $d = \frac{{{v^2}}}{{2a}}$

2. Michele_Laino

the requested time is given by the subsequent condition: $0 = v - at$ please solve that equation for time $$t$$. Of course $$v=108\;Km/h$$

3. anonymous

@Michele_Laino

4. anonymous

Thank you!!!!!!!!

Find more explanations on OpenStudy