Driving a Car on a Straight Road: Analyzing Forces

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In summary, the conversation discusses the forces involved in driving a car on a straight road, including engine torque, friction on the tires, and air resistance. It is determined that the total force required for the car to move is equal to the engine torque minus the air resistance and rolling friction. When the car is at rest, the minimum engine torque required to start the car is equal to the rolling resistance of the rear wheels plus the friction resistance on the front wheels. The conversation also addresses the confusion surrounding the concept of static friction and the difference between static and kinetic friction. In conclusion, the four main forces at play in driving a car on a straight road are engine torque, rear wheels rolling resistance, front wheels rolling resistance, and air resistance.
  • #1
impel123
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I am building a project,where you drive a car on a straight road.

The car has 3 kinds of forces:
1)Torque of engine in the wheels
2)Friction on the tyres
3)Force due to air resistance

If a car accelerating,and is front wheel drive,then the 2 front wheels have these forces:

<-------(Engine Torque)-------O------(Static friction)-------------->

and the rear wheels

<-------(Rolling friction)-------O


so car has these forces:

<---(Engine torque,rolling friction,air resistance force)--(CAR)--(Static friction force)---->

So,Whats the total force?

F=engine_torque-air_resistance-rolling_friction-static_friction ?

I read that static friction causes movement...so static friction is equal to engine torque?I am comfused.
 
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  • #2
impel123 said:
I am building a project,where you drive a car on a straight road.

The car has 3 kinds of forces:
1)Torque of engine in the wheels
2)Friction on the tyres
3)Force due to air resistance

If a car accelerating,and is front wheel drive,then the 2 front wheels have these forces:

<-------(Engine Torque)-------O------(Static friction)-------------->

and the rear wheels

<-------(Rolling friction)-------O


so car has these forces:

<---(Engine torque,rolling friction,air resistance force)--(CAR)--(Static friction force)---->

So,Whats the total force?

F=engine_torque-air_resistance-rolling_friction-static_friction ?

I read that static friction causes movement...so static friction is equal to engine torque?I am comfused.

I think it would make the problem more clear if you think of engine torque and static friction being in the same direction.

<---(Engine torque ~ Static friction force)--(CAR)--(rolling friction, air resistance)---->
 
  • #3
so,if engine torque on front wheels<=static friction then

F_total=Engine_torque-air_resistance-rolling_friction_in_rear_wheels

else ,if engine torque on front wheels>static friction then

F_total=Kinetik_friction_force_in_front_wheels-air_resistance-rolling_friction_in_rear_wheels


When car speed=0,what is the minimum engine torque to start the car to move?

F_minumum=rolling_resistance_rear_wheels+x
where x is friction resistance on the front wheels.

What is the x?rolling friction again?
 
  • #4
impel123 said:
so,if engine torque on front wheels<=static friction then

F_total=Engine_torque-air_resistance-rolling_friction_in_rear_wheels
It might also be a good idea to stop referring to the force as static friction.
Although technically correct, it's a bit confusing, as evidenced by your following statement:
else ,if engine torque on front wheels>static friction then
If the torque exceeds the static friction then you no longer have static friction, ie. your wheels will spin and you will have kinetic friction.
F_total=Kinetik_friction_force_in_front_wheels-air_resistance-rolling_friction_in_rear_wheels

When car speed=0,what is the minimum engine torque to start the car to move?
It would be equal to the force required to move the car.
F_minumum=rolling_resistance_rear_wheels+x
where x is friction resistance on the front wheels.

What is the x?rolling friction again?
Rolling friction is the resistance of a wheel being rolled over a surface.
 
  • #5
I can't understand what is the minimun engine torque required to move the car,if initialy car speed=0..there is no resistance?

when car speed is >0 then the rear wheels have rolling friction,and the front wheels static friction so

if speed>0 then
Ftotal=Engine_torque-air_resistance-rolling_friction_rear_wheels

else is speed =0 then
Ftotal=Engine_torque

Is this right?
 
  • #6
impel123 said:
I can't understand what is the minimun engine torque required to move the car,if initialy car speed=0..there is no resistance?
There is always resistance.
when car speed is >0 then the rear wheels have rolling friction,and the front wheels static friction so
The front wheels also have rolling friction.
if speed>0 then
Ftotal=Engine_torque-air_resistance-rolling_friction_rear_wheels
Basically. Yes.
else is speed =0 then
Ftotal=Engine_torque

Is this right?
I do not understand the question.
 
  • #7
then,if and front wheels and rear wheels have rolling resistance,when speed>0

Ftotal=Engine_torque-air_resistance-front_wheels_rolling_resistance-rear_wheels_rolling_resistance


if speed=0,which is the minimum engine torque required to start the car to move?

Why don't you answer my questions?

I need to know which are the forces in the car when speed>0 and which is the minimun
engine torque required to move the car if speed=0.

There are 4 kinds of forces:
1)engine torque
2)rear_wheels rolling resistance
3)front wheels rolling resistance
4)air resistance

Give me an answer please...
 

1. What forces are acting on a car when driving on a straight road?

When driving a car on a straight road, there are two main forces acting on the car: the driving force and the resistance force. The driving force is generated by the engine and propels the car forward, while the resistance force is caused by factors such as air resistance, friction from the road, and the weight of the car.

2. How does the driving force affect the motion of the car?

The driving force determines the acceleration of the car. A larger driving force will result in a greater acceleration, while a smaller driving force will result in a slower acceleration. This force is also responsible for maintaining the car's constant speed on a straight road.

3. What is the role of the resistance force in driving a car on a straight road?

The resistance force acts in the opposite direction of the driving force and is responsible for slowing down the car. It is important to consider the resistance force in order to maintain a steady speed on a straight road and to determine the amount of force needed to overcome it.

4. How does the weight of the car affect its motion on a straight road?

The weight of the car plays a role in determining the amount of resistance force acting on the car. The heavier the car, the more resistance force it will experience, making it more difficult to maintain a constant speed. This is why lighter cars tend to have better acceleration and top speed.

5. How can we analyze the forces acting on a car while driving on a straight road?

To analyze the forces acting on a car while driving on a straight road, we can use Newton's laws of motion. The first law states that an object will remain at rest or in constant motion unless acted upon by an external force. The second law states that force is equal to mass times acceleration. By understanding these laws and considering the driving and resistance forces, we can accurately analyze the motion of a car on a straight road.

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