Acceleration After Applied Force is Stopped?

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SUMMARY

The discussion centers on the phenomenon of a truck continuing to gain speed after the driver disengages the clutch at 25 mph. The user explains that while the engine's force becomes zero upon clutch engagement, the truck's acceleration does not drop instantaneously to zero due to the principles of physics. Instead, the acceleration decreases gradually, allowing the truck to momentarily increase its velocity before deceleration begins. The user also highlights the role of speedometer readings, which utilize a decaying average to smooth out fluctuations in speed measurement.

PREREQUISITES
  • Understanding of basic physics concepts such as acceleration and velocity.
  • Familiarity with the mechanics of manual transmission vehicles.
  • Knowledge of how speedometers function, particularly in terms of averaging measurements.
  • Basic grasp of forces acting on moving objects, including friction and inertia.
NEXT STEPS
  • Research the principles of Newton's laws of motion, particularly the second law regarding acceleration.
  • Explore the mechanics of manual transmission systems and how they affect vehicle dynamics.
  • Learn about speedometer technology and the methods used for averaging speed measurements.
  • Investigate the effects of friction and drag on vehicle acceleration and deceleration.
USEFUL FOR

Automotive enthusiasts, physics students, and anyone interested in understanding vehicle dynamics and the effects of clutch engagement on acceleration.

Guy
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I have a question that has been puzzling me for a while.

When I drive my truck and accelerate hard until 25 mph then put the clutch into roll freely, the truck will climb a few more mph before beginning to slow down. This is on flat ground or even a slight uphill.

The way I see it is as follows. Say acceleration of the truck is 5 ft/s2 (random number). Once the clutch is in the force from the engine is now 0, and therefore acceleration should be 0 unless there is another force pushing the truck forward. However in order to be continuous, acceleration cannot jump from 5 to 0, and will have to decrease continuously. While it is decreasing it is still positive and will cause velocity to climb slowly.

Can anyone explain the physics behind this?
 
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I assume that you are watching the speedometer to determine whether you are speeding up or slowing down.

In order to smooth out the readings so that the needle (or the digits) do not vary wildly, the number that is displayed will be some kind of decaying average of the most recent measured values.

As long as your current speed is still higher than the currently displayed average, that average will still be going up.
 
So its is not continuing to accelerate. Thanks for the answer that has bothered me for a while now!
 

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