+22 Felipe drives his car at a velocity of 28 m/s. He applies the brake, which slows the vehicle down at a rate of 6.4 m/s2 and causes it to slow to a stop. How long does it take for the car to stop? Round your answer to the nearest tenth.
Felipe drives his car at a velocity of 28 m/s. He applies the brake, which slows the vehicle down at a rate of 6.4 m/s2 and causes it to slow to a stop. How long does it take for the car to stop? Round your answer to the nearest tenth.
What we want is for the velocity to equal 0 m/s.
(Initial velocity) minus (acceleration times time) = 0
28 m/sec – [(6.4 m/sec2) • (t sec)] = 0
Let's subtract (6.4 m/sec2) • (t) from both sides.
28 m/sec = (6.4 m/sec2) • (t)
Divide both sides by (6.4 m/sec2) This is going to be tricky.
I'm going to call sec2 sec-sec so I can cancel one of them
Dividing by a term is the same as multiplying by the inverse of that term.
28 meter 1 sec-sec
––– ––––– • ––– ––––––
1 sec 6.4 meter
Cancel units
28 meter 1 sec-sec 28 sec
––– ––––– • ––– –––––– = –––––– = 4.375 sec, rounds to 4.8 sec
1 sec 6.4 meter 6.4
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