A car moves along an x axis through a distance of 900 m, starting at rest (at x = 0) and ending at

rest (at x = 900 m). Through the first ¼ of that distance, its acceleration is +2.25 m/s2
. Through
the rest of that distance, its acceleration is – 0.750 m/s2
. Find its maximum speed?

1 answer

You have to tackle these type of problem in steps: Solve for the first leg of the trip, and then solve for the second leg of the trip.

Use the following equation for the first leg of the trip:

Vf^2=Vi^2+2ad

Where

d=900m*(1/4)=225m
a=2.2 m/s^2
Vi=0m/s
and
Vf=?

Solve for Vf:

Vf^2=Vi^2+2ad

Vf^2=0+2(2.25m/s^2)*(225m)

Vf^2=1,012.5m^2/s^2

Vf=(1,012.5m^2/s^2)^1/2

Vf=31.8m/s^2

Vf for the first leg of the trip =Vi for the second leg of the trip. Solve for Vf of the second leg of the trip, which is the maximum speed of the trip.

Again, use the following equation for the first leg of the trip:

Vf^2=Vi^2+2ad

Where

d=900m*(3/4)=675m
a=0.750 m/s2
Vi=31.8m/s^2
and
Vf=?

Solve for Vf:

Vf^2=Vi^2+2ad

Vf^2=31.8m/s^2+2(0.750 m/s2)*(675m)

I'll let you do the rest.