# Is Thinking Distance Proportional to Speed in Car Braking?

• Lols
In summary, the conversation discusses the topic of braking distance for a car at different speeds, specifically at 30mph and 20mph. It is mentioned that the braking distance for a car at 30mph is 13.5m and at 20mph is 6.0m. The conversation also brings up the concept of thinking distance, which is directly proportional to speed. The question posed is to show that the thinking distance at 20mph is also 6.0m, but the given information does not include the necessary variables to do so. The conversation suggests using algebra to create equations that incorporate variables for thinking time and deceleration while braking. However, without additional information, it is not possible to accurately determine the
Lols
The braking distance for a car at 30mph is 13.5m and 6.0m at 20mph.
Thinking distance is directly proportional to speed. Show that the thinking distance at 20mph is 6.0 m. This question has baffled me, pls help

Lols said:
The braking distance for a car [is] 6.0m at 20mph.
... Show that the thinking distance at 20mph is 6.0 m.
I think you must have misstated the question.
When you've sorted that out, try to write a general equation for braking distance in terms of whatever variables you deem relevant.

I've check
haruspex said:
I think you must have misstated the question.
When you've sorted that out, try to write a general equation for braking distance in terms of whatever variables you deem relevant.
ed

Lols said:
I've checked
Ok, but it can't be right. I suggest we just do it algebraically, so put variables for the given data and ignore the actual values for now.
Create another unknown variable for each of:
- think time
- deceleration while braking
Using those, write equations corresponding to the given information.

The thinking distance at 20 mph could be 6 m if the thinking time happens to be 0.671 s. The thinking distance depends on the thinking time, which isn't given. It could be deduced from some other information such as the total stopping distance including the thinking distance for some speed. Might there be something like that given in another part of the question?

"Thinking distance" means the distance the car travels within the reaction time of the driver?
As the two given braking distances do not include that, I don't see how we could make any statement about that distance without additional assumptions.

## 1. What is force?

Force is a physical quantity that describes the push or pull on an object. It can cause an object to accelerate, decelerate, or change direction.

## 2. How is force measured?

Force is measured in newtons (N) using a device called a spring scale or force gauge. One newton is equivalent to the amount of force needed to accelerate one kilogram of mass at a rate of one meter per second squared.

## 3. What is the relationship between force and speed?

Force and speed have a direct relationship. An increase in force will result in an increase in speed, while a decrease in force will result in a decrease in speed. This relationship is described by Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it.

## 4. Can an object have a constant speed and changing force?

Yes, an object can have a constant speed and changing force. This is known as uniform circular motion, where the force acting on an object is directed towards the center of the circular path it is traveling on.

## 5. How does mass affect force and speed?

Mass has an indirect relationship with force and speed. A greater mass will require a greater force to accelerate it at the same rate as a smaller mass. However, once an object is in motion, its mass has no effect on its speed unless an external force is applied. This is described by Newton's first law of motion, also known as the law of inertia.

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