Betty weighs 436N and she is sitting on a playground swing seat that hangs 0.46 m above the ground. Tom pulls the swing back and releases it when the seat is 1 m above the ground. the acceleration of gravity is 9.8 m/s/s.
how fast is Betty moving when the swing passes through its lowest position? answer in units of m/s.
if Betty moves through the lowest point at 1.4 m/s, what is the magnitude of the work done on the swing by friction? answer in units of J
2007-10-31 11:22:00 · 1 answers · asked by lilprincess_2good4u 1 in Science & Mathematics ➔ Physics
Versus the bottom of the arc, Tom has given Betty and the swing some potential energy. (The problem doesn't give a mass for the swing itself, I guess it's massless.)
U = m*g*h
where m*g is Betty's weight and h = 1 m - 0.46 m
Do you know? Are you supposed to ignore friction for the 1st question? But then for the 2nd question there is friction? If so, set U = KE [(1/2)*m*v^2] and solve for V for the 1st question.
With friction, when Betty passes through the bottom of the arc, her speed is 1.4 m/s so her kinetic energy is
KE = (1/2)*m*v^2
where m = W/g. The difference between that and the original U is the work done by friction.
2007-10-31 15:27:27 · answer #1 · answered by sojsail 7 · 0⤊ 0⤋