Answer:
the space shuttle orbiting the Earth
Explanation:
Centripetal force is the force that keeps an object in circular motion around some fixed point. Different forces can act as source of centripetal force. Let's see which one in the options given:
the space shuttle orbiting the Earth --> in this case, the centripetal force is provided by gravity: the gravitational attraction between the Earth and the shuttle keeps the shuttle in circular orbit
a child on a merry-go-round --> in this case, friction acts a source of centripetal force, keeping the child along the circular trajectory
a bike rounding a curve --> the centripetal force is provided by the friction between the tires of the bike and the road
a book falling off a table --> this is not a circular motion, so there is no centripetal force.
According to what we have written above, the correct answer is
the space shuttle orbiting the Earth
