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Exercise 10.37 A 2.20 kg rock has a horizontal velocity of magnitude 12.0 m/s wh

ID: 1478311 • Letter: E

Question

Exercise 10.37

A 2.20 kg rock has a horizontal velocity of magnitude 12.0 m/s when it is at point P in the figure (Figure 1) .

Part A

At this instant, what is the magnitude of its angular momentum relative to point O?

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Part B

What is the direction of the angular momentum in part (A)?

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Part C

If the only force acting on the rock is its weight, what is the magnitude of the rate of change of its angular momentum at this instant?

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Part D

What is the direction of the rate in part (C)?

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Figure 1 of 1

Exercise 10.37

A 2.20 kg rock has a horizontal velocity of magnitude 12.0 m/s when it is at point P in the figure (Figure 1) .

Part A

At this instant, what is the magnitude of its angular momentum relative to point O?

L =   kgm2/s  

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Part B

What is the direction of the angular momentum in part (A)?

What is the direction of the angular momentum in part (A)? into the page out of the page

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Part C

If the only force acting on the rock is its weight, what is the magnitude of the rate of change of its angular momentum at this instant?

dL dt =   kgm2/s2  

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Part D

What is the direction of the rate in part (C)?

What is the direction of the rate in part (C)? into the page out of the page

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Figure 1 of 1

Explanation / Answer

a)

L = m r X v that is cross product of two vectors r and v

L = mvr sin(angle) = (2.2)(12)(8)sin(143.1degrees) = 126.8 kgm^2/s

b) Direction is into the page

c)

dL/dt = d[mvr sin(angle)] /dt = r d[mv sin(angle)] /dt
= (2.2)(12)(8)cos(143.1degrees) = (-168.89) kgm^2/s
dL/dt = r X F which is torque

d) Since there is negative sign direction is out of the page