A car starts from rest and travels for 6.0s with a uniform acceleration of 2.7m/s ^2. The driver then applies the brakes, causing a uniform acceleration of -2.0m/s^2. If the brakes are applied for 2.0s, determine each of the following.

Question

a.) how fast is the car going at the end of the braking period?

b.) how far has the car gone?

Answer 1

After six seconds, the car attains a velocity of 6*2.7 = 16.2 m/s, and will; have travelled a distance (a/2)*t^2 = 486 m.

Then the deceleration starts.

(a) After two seconds of deceleration,
V = 16.2 - 2.0*2 = 12.2 m/s

(b) Average speed during deceleration for 2 seconds = 14.2 m/s

Total distance travelled = 486 + 2*14.2 = 514.4 m

Answer 2

I believe 486 m should be 48.6 m

Answer 3

A car starts from rest and travels for 5.1 s with
a uniform acceleration of 3.6 m/s
2
. The driver
then applies the brakes, causing a uniform
acceleration of −1.3 m/s
2
.
If the brakes are applied for 2.1 s, how fast
is the car going at the end of the braking
period?
Answer in units of m/s.