# physics

A car and driver weighing 7750 N passes a sign stating “Bridge Out 28.5 m Ahead.” She slams on the brakes, and the car decelerates at a constant rate of 10.6 m/s2 .
The acceleration of gravity is 9.8 m/s2 .
What is the magnitude of the work done stopping the car if the car just stops in time to avoid diving into the water?

1. 👍 0
2. 👎 1
3. 👁 1,265
1. Using Newton's second law F=ma
to find the mass, then again the same law to find the frictional force.
Finally use Work done = F.D
Units are in kg, m/s² and J.

Mass m = 7750/9.8 = 790.82 kg
Frictional force = ma
= 790.82 kg * 10.6 m/s²
= 8382.7 N

Work done (assuming uniform frictional foce)
= F.D
= 8382.7 N * 28.5 m
= 238906 J
= 238.9 kJ

1. 👍 0
2. 👎 0

## Similar Questions

1. ### Physics

A car and driver weighing 7740 N passes a sign stating “Bridge Out 27.7 m Ahead.” She slams on the brakes, and the car decelerates at a constant rate of 12.3 m/s^2. The acceleration of gravity is 9.8 m/s^2. What is the

asked by Jess on February 14, 2015
2. ### physics

A driver of a 7550 N car passes a sign stating "Bridge Out 25 Meters Ahead." She slams on the brakes, coming to a stop in 10 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the weight

asked by jesse on October 19, 2010
3. ### PHYSICS

A driver of a 7400 N car passes a sign stating "Bridge Out 30 Meters Ahead." She slams on the brakes, coming to a stop in 10 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the weight

asked by spencer on October 24, 2010
4. ### physics

A driver of a 7550 N car passes a sign stating "Bridge Out 25 Meters Ahead." She slams on the brakes, coming to a stop in 10 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the weight

asked by jesse on October 19, 2010
5. ### physics

A driver of a 7100 N car passes a sign stating "Bridge Out 30 Meters Ahead." She slams on the brakes, coming to a stop in 10 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the weight

asked by Steve on October 18, 2009
1. ### physics

A driver of a 7550 N car passes a sign stating "Bridge Out 25 Meters Ahead." She slams on the brakes, coming to a stop in 10 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the weight

asked by jesse on October 19, 2010
2. ### physics

A driver of a 7.50 N car passes a sign stating "Bridge Out 30 Meters Ahead." She slams on the brakes, coming to a stop in 10.0 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the

asked by Anonymous on October 21, 2007
3. ### Physics

I really cannot understand how to get to the answer. Thank you! Two cars are traveling, Car A is behind the other, on a straight road. Each has a speed of 21 m/s and the distance between them is 25 m. The driver of the rear car

asked by Darius on September 24, 2018
4. ### physics

A driver of a car travelling along a straight road with a speed of 72k.m./hour . Observes a sign board which gives the speed limit 54k.m./h.the signboard is 70m ahead when the driver applies break . Calculate the acceleration the

asked by pari on June 10, 2014
5. ### English

Posted by rfvv on Friday, June 10, 2016 at 11:32pm. 1. The building of the new bridge will go ahead as planned. 2. The building of the new bridge will go ahead as it is planned. (Does #1 mean #2? Is 'it is' deleted?) 3. Lee was

asked by rfvv on June 13, 2016

More Similar Questions