# Calculating Force Needed to Stop a Moving Vehicle

• JPhysic
In summary: F=M x AW=14570x10=145700 NW=14570x20=29140 NW=14570x30=43710 NW=14570x40=58280 NW=14570x50=72850 NW=14570x60=871920 NW=14570x70=101990 N
JPhysic

## Homework Statement

I am just enquiring about car brakes, and figuring out how much force needs to be applied to stop a moving object (car).

## Homework Equations

1457Kg – Curb weight of the car (overall mass)

F = M x A

1457kg x 10mph = 14570 (Newtons)
1457kg x 20mph = 29140 N
1457kg x 30mph = 43710 N
1457kg x 40mph = 58280 N
1457kg x 50mph = 72850 N
1457kg x 60mph = 87420 N
1457kg x 70mph = 101990 N

## The Attempt at a Solution

So I've figured out the acceleration, but I need to find out, how much force needs to be applied to bring the car to a stand still using 312 Diameter brake disks. Would it be equal to or greater than the Acceleration?

JPhysic said:

## Homework Statement

I am just enquiring about car brakes, and figuring out how much force needs to be applied to stop a moving object (car).

## Homework Equations

1457Kg – Curb weight of the car (overall mass)

F = M x A

1457kg x 10mph = 14570 (Newtons)
1457kg x 20mph = 29140 N
1457kg x 30mph = 43710 N
1457kg x 40mph = 58280 N
1457kg x 50mph = 72850 N
1457kg x 60mph = 87420 N
1457kg x 70mph = 101990 N

## The Attempt at a Solution

So I've figured out the acceleration, but I need to find out, how much force needs to be applied to bring the car to a stand still using 312 Diameter brake disks. Would it be equal to or greater than the Acceleration?

I believe you will need the coefficient of friction (dynamic) between the brake pads and the rotors. Why would you need that?

And you will probably need to do an integration from the inside to the outside of the swept radius of the rotor, since the braking torque contribution will ratio with the radius.

I'm sorry my friend, but you just confused the hell out of me...

JPhysic said:
I'm sorry my friend, but you just confused the hell out of me...

Perhaps I misinterpreted your question. I thought you were asking how hard (how much force) you have to squeeze the brake pads together on the rotor in order to brake a car to a standstill. Were you asking something different?

The "brakes" do not apply force directly to a car in a linear fashion. The brake pads sqeezing the rotors apply a braking torque to the wheels, which is what slows the car down...

I need to know at:

10mph - 70mph with a mass at 1457Kg, what force is needed to bring the car to a stand still

JPhysic said:
I need to know at:

10mph - 70mph with a mass at 1457Kg, what force is needed to bring the car to a stand still

F = M x A

1457kg x 10mph = 14570 (Newtons)
1457kg x 20mph = 29140 N
1457kg x 30mph = 43710 N
1457kg x 40mph = 58280 N
1457kg x 50mph = 72850 N
1457kg x 60mph = 87420 N
1457kg x 70mph = 101990 N

Well, first of all, you don't multiple mass in kg by speed in mph to get force in Newtons.

And you don't multiply mass by speed to get force anyway.

You wrote the equation F=MxA, which is correct. You also need the equation W=FxD (work equals force multiplied by distance). Now, write the equations, and keep your units consistent (use mks units).

## 1. What is the formula for calculating the force needed to stop a moving vehicle?

The formula for calculating the force needed to stop a moving vehicle is force = mass x acceleration. This is also known as Newton's second law of motion.

## 2. How do you determine the mass of a moving vehicle for this calculation?

The mass of a moving vehicle can be determined by weighing the vehicle or by obtaining the weight from its specifications.

## 3. What is the acceleration value used in the calculation?

The acceleration value used in the calculation is the deceleration rate, which is usually given in meters per second squared (m/s^2). This value can be obtained from the vehicle's braking system or by conducting a deceleration test.

## 4. Can the force needed to stop a moving vehicle be affected by external factors?

Yes, the force needed to stop a moving vehicle can be affected by external factors such as road conditions, tire traction, and air resistance. These factors can increase or decrease the amount of force required to stop the vehicle.

## 5. Is the force needed to stop a moving vehicle always the same?

No, the force needed to stop a moving vehicle can vary depending on the weight and speed of the vehicle, as well as external factors such as road conditions. A heavier or faster moving vehicle will require more force to stop compared to a lighter or slower moving vehicle.

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