posted by george .
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.
a.) how fast is the car going at the end of the braking period?
b.) how far has the car gone?
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