Posted by **johnny** on Tuesday, February 15, 2011 at 6:12pm.

A driver of a car going 95.0 km/h suddenly sees the lights of a barrier 39.0 m ahead. It takes the driver 0.95 s before he applies the brakes, and the average acceleration during braking is -10.0 m/s2.

What is the maximum speed at which the car could be moving and not hit the barrier 39.0 m ahead? Assume the acceleration rate doesn't change.

- Physics -
**drwls**, Tuesday, February 15, 2011 at 6:28pm
Ignore the 95.0 km/h speed of the driver. He may hit the barrier. They want you to calculate the speed V for which the stopping distance would be exactly 39.0 m.

The stopping distance will be

V*0.95 + (V/{a})*(V/2) = 39.0 m

Solve for V.

The second term, V^2/(2|a|)

is the distance travelled with brakes applied, It equals the average speed times the time spent braking. The first term, V/0.95s, it the distance travelled before the brakes are applied,

- Physics -
**johnny**, Tuesday, February 15, 2011 at 6:32pm
Can you go through and show all work to the finish?

## Answer This Question

## Related Questions

- Physics - A driver of a car going 95.0 km/h suddenly sees the lights of a ...
- Physics - A driver of a car going 90.0km/h suddenly sees the lights of a barrier...
- physics - The driver of a car going 90.0 km/h suddenly sees the lights of a ...
- Physics - A driver of a car going 90 km/h suddenly sees the lights of a barrier ...
- Physics - The driver of a car is going 90 km/hr suddenly sees a barrier40m ahead...
- Physics - a driver of a car going 95.0km/h suddenly sees the lights of a barrier...
- Physics - What is the maximum speed at which a car could be moving and not hit a...
- Physics - What is the maximum speed at which a car could be moving and not hit a...
- physics - A car starts from rest and travels for t1 seconds with a uniform ...
- physics - A car is traveling at 20.8 m/s when the driver sees a dog run out into...

More Related Questions