A ball of mass m is released from rest at the top of a roof. The ball slides along the roof without friction. The roof m

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A ball of mass m is released from rest at the top of a roof. The
ball slides along the roof without friction. The roof makes an
angle α with respect to the vertical.
(a) By writing the Newton’s second law along the roof, write the
equation of motion describing the motion of the ball.
(b) Solve the equation of motion.
(c) Write the expression of the final time tf when the ball
reaches the edge of the roof of length L, and thus express the
velocity at tf (without tf in the expression).