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Describe a situation in which the net external force is not zero, but its speed remains constant.
I don't know if this situation is possible to explain.
I don't know if this situation is possible to explain.
Good. Note the key word velocity. How does that differ from speed?An object stays at rest, or if in motion, stays in motion at a constant velocity unless acted on by a net external force.
Exactly! So see if you can try to answer the question now.Velocity has both magnitude and direction but speed doesn't have direction
How about a car following any curved path while moving at constant speed? A section of road could be similar to a sine wave, ellipse, spiral, parabola, ..., and a car would be able to follow that path while moving at constant speed.A car going in a circle.
Your answer is definitely correct!A car going in a circle.
Do you remember the expression for centripetal acceleration?Ok so what is the net external force acting on the car?
That would be speed^2 / (radius of curvature), which gets complicated for paths other than a circle.Do you remember the expression for centripetal acceleration?
The simple answer is that centripetal force = centripetal acceleration x mass of the car.Yes. So centripetal force that pulls it toward the center is external?