# Find Speed of car based on stopping distance and decceleration.

• aprymek
In summary, to calculate the speed of a car, you can use the formula: Speed = (Stopping distance x Deceleration) / 2. The safe deceleration rate for a car depends on various factors, but on average, a deceleration rate of 7-8 meters per second squared is considered safe. Even if only the stopping distance is known, the speed of a car can still be determined, though other factors will also affect the calculation. The higher the speed of a car, the longer its stopping distance will be due to the need to dissipate more kinetic energy through braking. The deceleration rate can vary for different cars, depending on factors such as weight, tire condition, braking system, driver's
aprymek
1. A car leaves skid marks 85 meters long. It slows down at a rate of 4m/s^2. How fast was the car traveling?
Again, totally confused. Don't know where to start.

You must show some attempt at working the problem to receive help. Could you explain what part is confusing you? What kinematic equations do you think would fit the information you are given?

To find the speed of the car, we can use the equation: v^2 = u^2 + 2as, where v is the final velocity, u is the initial velocity, a is the acceleration, and s is the stopping distance.

In this case, we know that the stopping distance (s) is 85 meters and the acceleration (a) is -4m/s^2 (since the car is slowing down). We can rearrange the equation to solve for the initial velocity (u).

u = √(v^2 - 2as)

Plugging in the known values, we get:

u = √(0 - 2(-4)(85))

u = √(0 + 680)

u = √680

u ≈ 26.08 m/s

Therefore, the car was traveling at a speed of approximately 26.08 meters per second before it started slowing down.

## 1. How do you calculate the speed of a car based on its stopping distance and deceleration?

To calculate the speed of a car, you can use the formula: Speed = (Stopping distance x Deceleration) / 2. You will need to know the stopping distance in meters and the deceleration in meters per second squared.

## 2. What is considered a safe deceleration rate for a car?

The safe deceleration rate for a car depends on various factors such as the road conditions, weather, and type of vehicle. However, on average, a deceleration rate of 7-8 meters per second squared is considered safe for most cars.

## 3. Can the speed of a car be determined if only the stopping distance is known?

Yes, the speed of a car can be determined if only the stopping distance is known. However, other factors such as the weight of the car, road conditions, and braking efficiency will also affect the speed calculation.

## 4. How does the speed of a car affect its stopping distance?

The higher the speed of a car, the longer its stopping distance will be. This is because the car will have more kinetic energy that needs to be dissipated through braking, resulting in a longer distance required to come to a complete stop.

## 5. Is the deceleration rate the same for all cars?

No, the deceleration rate can vary depending on the type and condition of the car. Factors such as the weight, tire condition, and braking system can affect the deceleration rate of a car. Additionally, the driver's reaction time and braking technique can also impact the deceleration rate.

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