Question

the velocity of a car changes from 20 m/s east to 5 m/s east in 5 seconds what's the acceleration of the car

Answer 1

To solve this remember a=change in v/t, assuming the direction for the velocity, is + positive east. You can calculate it simply by this. A=v/t= A=5-20/5= A=-15/5= A=-3m/s squared. Change in velocity= vf-vi.