Question of the Day

Which of the following examples has a net force of zero acting on the object?

A seat in a Ferris wheel constantly going in circles
A pendulum coming to a rest
Opening a glass soda top

Solution: I: Doesn’t qualify because even though the seat is going at a constant speed, its direction is always changing, so its velocity is also always changing II: Since the pendulum comes to a stop, some kind of friction is affecting it; thus, net force is not equal to zero III: Even though the top is opened, neither the person nor the top actually moves permanently. Since its not moving after being opened, velocity is constant (at zero). Why the other choices are wrong: You either didn’t recognize the change in direction or friction force.

A) I only B) I and II C) I and III D) III only E) I, II and III

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