Bridge physics and a record player. and explain your reasoning. All problem part

Question

Bridge physics and a record player. and explain your reasoning. All problem parts on this page will count or be dropped together as one. A student flicks a small (m = 50.0 g) rock off the concrete deck of the Westover Bridge while another student records a video of this experiment. The video shows the rock leaving the bridge and falling into the Monongahela River below. Later, they take the video to their physics instructor, who helps them determine two pieces of data about the experiment: The initial velocity of the rock v vector_0 was 3.22 m/s (perfectly horizontal) and the rock hits the water at t = 2.75 s after it left the deck. Neglect whatever air friction the rock may experience and use g = 9.80 m/s^2. a. Determine the vertical distance, in meters, between the deck of the bridge and the surface of the water. b. What is its kinetic energy, in Joules, just before impact?

Explanation / Answer

Q.1 we will use kinematic equation,

h = ut + 1/2 gt^2

h = 3.22 ( 2.75) + 0.5 (9.8) ( 2.75^2) = 8.855 + 37.05625= 45.91125 m apprx

b) let's find the velcity before impact

v^2 = 3.22 ^2 + 2 (9.8) ( 45.91125) = 910.23

KE before imact = 0.5 ( 50 x 10^-3 ) ( 910.23 ) = 22.7557 J

c) energy = work done to overcome friction

22.7557 J = F ( 5 x 10^-2 m)

F = 455. 11 N

d) L (angular momentum) = I w

angular momentum is conserved in the absence of external force

so if w ( angular speed slows down), I will increase to conserve the angular momentum

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