physics
posted by stephanie
Calculate the force needed to bring a 1070–kg car to rest from a speed of 89.0 km/h in a distance of 110 m (a fairly typical distance for a nonpanic stop).
2.97×103 N correct answer
Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in 2.34 m. Calculate the force exerted on the car and compare it with the force found in part (a).
Force = 1.40×105 N
Ratio = 47.0
correct answer
what are the steps to get these answers?

Damon
force = mass * acceleration
now the kinematics
first units
89 km/h * 1000 meters/km * 1 h/3600 seconds
= 24.7 meters/second
average speed during stop = 24.7/2 = 12.36
so how long did it take?
t = 110 meters/12.36 m/s
= 8.9 seconds to stop
acceleration assumed constant so it is
a = 24.7 m/s / 8.9 s
a = 2.78 m/s^2 (about 1/3 acceleration of gravity)
F = 1070*2.78 = 2975 N
so we agree
Now do all that for 2.34 meters (OUCH!!)
t = 2.34 meters/12.36 m/s
= .1893 seconds
a = 24.7/.1893 =  130 m/s^2
( about 13 times gravity !!! )
F = 1070 * 130 = 139,599 N
139599/2975 = 46.9
Respond to this Question
Similar Questions

Physics
A race car can be slowed with a constant acceleration of 11 m/s^2 a. If the car is going 55 m/s, how many meters will it travel before it stops? 
Physics
A 1100 kg car is moving toward the north along a straight road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to rest in a distance of 140 m. (a) If the road is completely level, what is the constant force … 
Physics
A 1100 kg car is moving toward the north along a straight road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to rest in a distance of 140 m. (a) If the road is completely level, what is the constant force … 
Physics
A 1000kg car is driving toward the north along a straight road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest in a distance of 140 m. What is the constant force applied to the car to bring it to … 
physics
A force of 9000 N is used to stop a 1500kg car traveling at 20 m/s. What braking distance is needed to bring the car to a halt? 
Physics
A car travels at 64 mi/h when the brakes are suddenly applied. Consider how the tires of a moving car come in contact with the road. When the car goes into a skid (with wheels locked up), the rubber of the tire is moving with respect … 
Physics
Calculate the force needed to bring a 1100–kg car to rest from a speed of 83.0 km/h in a distance of 118 m (a fairly typical distance for a nonpanic stop). Suppose instead the car hits a concrete abutment at full speed and is brought … 
Physics
A force of 9000N is used to stop a 1500 kg car traveling at 20m/s. What braking distance is needed to bring the car to a halt? 
physics
Calculate the force needed to bring a 1070–kg car to rest from a speed of 89.0 km/h in a distance of 110 m (a fairly typical distance for a nonpanic stop). Suppose instead the car hits a concrete abutment at full speed and is brought … 
Physics
A force of 7500 N is used to stop a 2000kg car traveling 25m/s. What breaking distance is needed to bring the car to a halt?