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Difficulty: MediumDriveshafts and Differentials

A truck equipped with a standard open rear differential stops with one rear tire resting on dry asphalt and the other rear tire on a patch of smooth ice. What happens at the drive wheels when the driver presses the accelerator pedal to move forward?

  1. A
    The differential automatically transfers engine torque away from the slipping wheel to the tire on dry asphalt.
  2. The tire on the ice spins rapidly while the tire on the dry asphalt receives little driving force and stays stationary.Answer
  3. C
    Both rear tires lock together and rotate at identical speeds regardless of surface traction.
  4. D
    The suspension dampening system stiffens to mechanically bind the axle shafts together.

Answer

The tire resting on the ice will spin freely while the tire on the dry asphalt receives negligible torque and remains stationary.
A standard open differential always distributes equal torque to both drive wheels. Because torque output on both sides is limited by whichever wheel has the least amount of road resistance, the tire on ice spins easily while the tire on high-traction pavement does not receive enough torque to propel the vehicle.

Step-by-Step Solution

1
Analyze how an open differential distributes torque between drive wheels.
An open differential always applies equal torque (50%/50%50\% / 50\%) to each drive axle.
The differential spider gears pivot inside the carrier, balancing rotational force evenly across both axle side gears.
2
Evaluate the torque limit imposed by the wheel on ice.
The tire on smooth ice has almost zero traction and can only support minimal torque before spinning out.
Torque delivery to both wheels is limited to whatever torque the wheel with the least grip can generate against the ground.
3
Determine the resulting motion at both wheels.
The spider gears rotate rapidly around the stationary side gear of the high-traction wheel, driving only the slipping axle.
Power follows the path of least resistance, leaving the gripping tire without sufficient torque to move the vehicle.

Key Concept

Open Differential Torque Distribution under Asymmetric Traction
Estimated Time:1m 0s
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Topics

Driveshafts and Differentials

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