How long does it take to stop the car

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In summary, the time it takes to stop a car depends on various factors such as the speed of the car, the condition of the road, and the driver's reaction time. On average, it takes about 4-5 seconds to come to a complete stop from a speed of 60 miles per hour on a dry road. However, this time can increase significantly if the road is wet or slippery. It is important for drivers to maintain a safe distance from other vehicles and to reduce their speed when approaching a stop to ensure a timely and safe stop.
  • #1
bob4000
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if a car is moving at 14m/s, and the coefficient of friction is 0.8, what is the distance it takes to stop the car after the brakes are applied locking all four wheels?
 
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  • #2
The first step in the problem is to draw your free-body diagram and label all of the forces acting on the car.
Basically you have 3 forces, the force of the weight, the force of friction, and the normal force on each tire.
Because each of these forces are the same on each wheel it is only neccesary to draw the FBD for one wheel.
After you draw your FBD set up your force equation in each direction. In this case the car is is only moving in 1 direction call it the positive X direction.
So you have your sum of the forces in the X direction equation.
4f=ma
where is the friction force

solve that equation for a and then use the kinematic equation Vf^2=Vi^2+2*a*d

with Vf=0 solve for d
 
  • #3

1. How long does it take to stop a car in an emergency?

The stopping distance of a car in an emergency depends on various factors such as the speed of the car, the road conditions, and the condition of the brakes. On average, it takes about 1.5 seconds to react and another 3 seconds to completely stop a car traveling at 60 miles per hour. This means the total stopping distance can range from 90 to 120 feet.

2. How does the weight of a car affect its stopping distance?

The weight of a car directly affects its stopping distance. A heavier car has more momentum and requires more force to stop, resulting in a longer stopping distance. It is estimated that for every additional 500 pounds of weight, the stopping distance increases by 20 feet.

3. Can the type of tires impact the stopping distance of a car?

Yes, the type of tires can significantly impact the stopping distance of a car. Tires with a better grip and tread can reduce the stopping distance by providing more friction between the tires and the road. On the other hand, worn out or under-inflated tires can increase the stopping distance and make it more difficult to stop the car quickly.

4. Is it possible to stop a car without brakes?

Yes, it is possible to stop a car without brakes, but it is not recommended. Some cars have emergency braking systems that can be activated by pulling a lever or pressing a button. In the absence of such systems, one can use the handbrake or downshift to a lower gear to slow down the car. However, these methods will not stop the car as quickly as using the brakes.

5. What should I do if the brakes fail while driving?

If the brakes fail while driving, the first thing to do is to stay calm and try to slow down the car gradually by downshifting to a lower gear. Then, turn on the hazard lights to alert other drivers. Look for an escape route, such as a side road or an open field, and try to steer the car in that direction. If all else fails, use the emergency handbrake to stop the car. It is important to remain focused and avoid any sudden movements that can cause the car to lose control.

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