A 15 kg, 1 m wide door which has frictionless hinges is closed but unlocked. A 400 g ball hits the exact middle of the door at a velocity of 35 m/s and bounces off elastically, thereby causing the door to slowly swing open. How long in seconds does it take for the door to fully open (rotate 90 degrees)?
Physic problem(2)...Please help - steven lou, Tuesday, May 21, 2013 at 7:35pm
Physic problem(2)...Please help - Anonymous, Tuesday, May 21, 2013 at 10:00pm
no. wrong answer
Physic problem(2)...Please help - Elena, Wednesday, May 22, 2013 at 4:38am
In vector form:
Δp⃗ =p₂⃗-p₁⃗ =mv₂⃗-mv₁⃗,
Δp =p₂-(-p₁) =mv₂+mv₁= 2mv.
The speed of the center of the door is
u=2mv/M=2•0.4•35/15 = 1.37 m/s
Its angular speed is
ω=u/r=2u/L =2. •1.87/1 = 3.73 rad/s
t= φ/ ω =π/3.73 = 0.84 s.
pyhsic - anonymous, Wednesday, May 22, 2013 at 7:10am
wrong answer Elena
Physic problem(2)...Please help - Anonymous, Thursday, May 23, 2013 at 4:52am