A car starts from rest and travels for 4.9 s with a uniform acceleration of +1.8 m/s2. The driver then applies the brakes, causing a uniform acceleration of -1.7 m/s2. The breaks are applied for 1.50 s.

Question

A car starts from rest and travels for 4.9 s with a uniform acceleration of +1.8 m/s2. The driver then applies the brakes, causing a uniform acceleration of -1.7 m/s2. The breaks are applied for 1.50 s.
1) How fast is the car going at the end of the breaking period?
2) How far has the car gone from its start?

bobpursley · Answer

Lets look at momentum.

The impulse equation ought to equal the final momentum.

F1*time1+F2*time2=mass*vfinal
but Force= mass*acceleration.
mass*1.8*4.9-mass*1.7*1.5= mass*Vfinal
solve for Vfinal.

How far?
distance= avg velocity*time
= Vf/2 * (1.5+4.9)