What force causes a car to accelerate?

Question

The gas pedal, gasoline, the engine, horsepower, gravity, are not the right answer. It is an external force.

My teacher say's it is an external force but would not say what is exerting the force.

Answer 1

The accelerative external force is the earth pushing forward against the tires, coupled to them by traction. This is the reaction force referred to in Newton's 1st law. The action it is a reaction to is the backwards push of the tires, via traction, on the earth.

Answer 2

My own definition of the Universal cause of motion is that in order for something to move it must receive a push.

So a parachutist falling down out of the sky is receiveing a push from an external system. Other wise he would never come down.According to relativity all forces are fictitious. They exist only when interaction of two masses occurs

When you push a car so that it will move it increases velocity as you apply more power to your push.
As the velocity increase each time the acceleration decrease to the point your wont feel a force between you and the car you are pushing .So acceleration is a decaying funtion whereas velocity is an increasing function as power is applied to effect the motion.

Once the car is moving at maximum velocity max Kinetic energy is born.
Kinetic energy does not exit till an object is in motion.

Forces are not the cause of acceleration but rather the acceleration is the cause of the forces which are usally borne in Pairs.
So force cannot come into existance during an interaction as a single force. They come in pairs but are borne in opposite direction.
NOw Power is another question.

Answer 3

I don't know if it's meant as a trick question (from your teacher). The mechanism of a car, to put simple (on gasoline engine, not diesel engine):

Gasoline is injected to combustion chamber. Spark plug makes spark, igniting the gasoline, causing it to explode (due to high pressure in combustion chamber). The explosion causes the camshaft to turn. The camshaft causes the wheel axle to turn, causing the the wheels to start rolling, and your car moves (either forward or backward). Gas pedal is used to control the amount of gasoline injected to combustion chamber. The more gasoline, the bigger the explosion, and the faster the camshaft turn, making the car go faster. When you step on the pedal, the machine injects more and more gasoline to the chamber, causing it to have bigger and faster explosion, which in turn making the car go faster and faster. And we experienced acceleration.

If it were a trick question, than all I can think of the answer is the friction force between the surface of the car's wheels and the surface of the street. If there are no friction force, your car would not move an inch, even though the wheels are spinning.

Answer 4

Well either your teacher isn't a physicist or it is a trick question. Acceleration is the change in an object's (the car) speed over time relative to the observational reference. If you take the observational reference as the road or similar, then the forces that contribute to the car's acceleration are the internal combusion of the engine, the transfer of energy through the crankshaft and transmission to the axle and tires. Then there is the coefficient of friction between the tires and the road in respect to gravity and the car's mass, all of which contribute to the acceleration of the car. So in essence, there is no definative answer here.

Answer 5

Torque and gearing/traction and overcoming friction and gravity (gravity on hills) Horsepower is the measure of the work in which an engine can do (like lets say 800 lb torque @2000 RPM on a 1ft wheel is the same horsepower as a 400 lb torque @4000RPM on a 1 ft wheel) even though the 800 pound foot engine is 2X as strong and the 400 one is 2X as fast

Answer 6

The force your foot is applying to the accelerator. Usually, if a teacher gives you a question like this, it's carefully worded and in the context of what you've been studying or are about to study. Try telling us the exact wording of the question and what you're studying.

Answer 7

Self-adjusting reaction forces and frictional forces between the partitions and flooring of the motor vehicle make the products in thea motor vehicle stick to its acceleration rather it is going to become the acceleration of the finished device.

Answer 8

In neutral, on a hill, the answer would be gravity.

You can also use the accelerator, the brake or the steering wheel to affect acceleration. (Remember velocity and acceleration are vectors so a change in direction is a change in velocity and therefore acceleration.)

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The answer your teacher might be looking for is *friction* necessary for traction to get the car to accelerate.

Answer 9

Horsepower ?

Answer 10

With my car, mainly force of habit.