Homework Help: physics

Posted by Anonymous on Monday, September 28, 2009 at 11:14pm.

A car is traveling 20 m/s when the driver sees a child standing on the road. He takes 0.8 s to react, then steps on the brakes and slows at 7.0 m/s2. How far does the car go before it stops?

physics - MathMate, Tuesday, September 29, 2009 at 8:23am
reaction time = 0.8 seconds at 20 m/s
distance = 0.8 s * 20 m/s = 16 m.

From v0²-v² = 2aS
where v0 and v are initial and final velocities,
a, acceleration
S, distance travelled

braking distance
= (0-20²)/(2*(-7 m/s²))
= 40.8 m.

Total distance = ?
physics - gyted, Thursday, February 2, 2012 at 10:10pm
40.8

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