Stopping forces in an emergency stop

In summary, the conversation discusses calculating the forces applied during an uncontrolled stop of an object using winches and brakes. The necessary information needed includes the mass of the load, torque and lever arm length of the brakes, and the spring constant of the system. The elasticity of the rope is also a factor to consider. The method for finding the spring constant is explained, along with the equation for calculating peak force.
  • #1
simonwait
Hi

I'm trying to calculate the forces applied when suddenly stopping an object. I have a pair of winches which lowering an object at 400mm/s and would normally decelerate to a stop at 150mm/s^2. If the Estop for this winch is hit then we decelerate at 2000mm/s^2. However, if the power is pulled then the brakes are applied instantly and stop at whatever time it takes the brakes to arrest the load. There are 2 brakes both at 75Nm of torque on each winch one after the other on the output shaft so four brakes in total (not sure if having double brakes makes a difference).

What I am trying to figure out is what the force is during this uncontrolled stop and how far the load would travel in that time.
 
Physics news on Phys.org
  • #2
I think the information is incomplete. For the brakes that you know the deceleration rate, you need to know how much mass is being decelerated before you can calculate the brake force. For the 2 brakes where you know the torque, you need to know the lever arm length (or the gear radius). Also, it's not clear which information is relevant to the "uncontrolled stop" that you are trying to figure out.
 
  • #3
Oh sorry - I put that in and then seemly deleted it. The load is 1600kgs, The output shaft radius is 12mm. The 150mm/s^2 and 2000mm/s^2 show normal conditions and controlled stops, I am trying to find an uncontrolled stop - ie like pulling the power so the motor locks up and the brakes instantly apply. I assume there will be a short amount of time where the inertia will drag the brake through the load.
 
  • #4
I am sure the 'spring constant' or resilience of the rope is very relevant here. The can make a massive difference to the peak force involved. If the rope temporarily stretches by double the distance when the brake is applied then the extra force could be halved.
 
  • #5
You know the torque the brakes can apply so if you know the drum diameter you can calculate the stopping force and deceleration.

I agree the elasticity of the rope will be a factor.
 
  • #6
You need the spring constant of the entire system to solve this problem. Imagine the load hanging freely at zero speed. You pull the load downward with a force, and measure the resulting movement. Divide the applied force by the amount of movement, and you get the spring constant. You can also calculate the spring constant from the sum of winch rope stiffness and length, shaft diameter and length, and gear train stiffness.

Then calculate the kinetic energy of the moving load just before the brake is applied. Equate that to the equation for spring potential energy: KE = 1/2 * K * x^2, where:
KE = kinetic energy
K = spring constant
x = peak displacement of the spring (how far the load moves after the brake is applied)

Peak force is then K * x.
 

1. What are stopping forces in an emergency stop?

Stopping forces in an emergency stop refer to the forces that act on a moving object to bring it to a stop in the shortest possible distance. These forces are typically exerted by the brakes of a vehicle or the friction between a moving object and the surface it is traveling on.

2. How do stopping forces affect an emergency stop?

Stopping forces play a crucial role in an emergency stop as they determine how quickly an object can be brought to a stop. The greater the stopping forces, the shorter the stopping distance will be. This is why vehicles with stronger brakes and better traction are able to stop more quickly in emergency situations.

3. What factors can affect stopping forces in an emergency stop?

There are several factors that can affect stopping forces in an emergency stop, including the speed of the moving object, the weight and size of the object, the condition of the brakes or tires, and the friction between the object and the surface it is traveling on. Environmental factors such as wet or icy roads can also impact stopping forces.

4. How can stopping forces be increased in an emergency stop?

Stopping forces can be increased by increasing the friction between the object and the surface it is traveling on. This can be achieved by using anti-lock brakes, which allow the wheels to maintain contact with the ground and prevent them from locking up. Additionally, maintaining a safe distance from other vehicles and reducing speed can also increase stopping forces in an emergency stop.

5. What are the risks of insufficient stopping forces in an emergency stop?

If stopping forces are insufficient in an emergency stop, the object may not be able to come to a complete stop in time, resulting in a collision or other dangerous situation. This can lead to injuries or property damage. It is important to regularly maintain and check the brakes and tires of a vehicle to ensure that stopping forces are sufficient in emergency situations.

Similar threads

Help with question on motion: Avoiding a rear-end collision
    • Introductory Physics Homework Help
Replies
6
Views
726
Tension in a Rope from Lowering Down and Friction Braking Torque at Stop
    • Introductory Physics Homework Help
Replies
3
Views
1K
Calculate Braking Torque for Winch Emergency Stop
    • Mechanical Engineering
Replies
2
Views
2K
Automotive How to calculate hydraulic disc brake size using actuation force?
    • Mechanical Engineering
Replies
15
Views
5K
The physics of braking on a motorcycle (manual transmission)
    • Mechanics
2
Replies
44
Views
6K
How Far Will the Glasses Land from the Stopped Bicycle?
    • Introductory Physics Homework Help
Replies
2
Views
1K
Finding net force from acceleration, speed and distance
    • Introductory Physics Homework Help
Replies
13
Views
2K
Calculating Force from Stopping in Gravity: Help Appreciated
    • Introductory Physics Homework Help
Replies
1
Views
526
Calculating Stopping Distance for a Small Buggy Using a Linear Actuator?
    • Mechanical Engineering
Replies
4
Views
3K
Basic Kinematics Questions, first year physics
    • Introductory Physics Homework Help
Replies
15
Views
5K

Hot Threads

Recent Insights

Back
Top