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Which is true about elastic collisions:

A straightforward method of finding the density of an object is to measure its mass and then measure its volume by submerging it in a graduated cylinder. What is the density of a 240-g rock that displaces 89.0 mL of water?

What is the absolute pressure at a depth of 9.73 m below the surface of a deep lake?  Take 1.01 x 105 Pa as atmospheric pressure.

A force of 300 N is applied 20 cm from the pivot point at an angle of 30o.  What is the torque?

For which case will the flow rate increase for Poiseuille flow?

After an average acceleration of 3.39 m/s2 during 2.29 s, a car reaches a final velocity of 16.1 m/s.  Find the car’s initial velocity.

A 129-kg horizontal platform is a uniform disk of radius 1.61 m and can rotate about the vertical axis through its center. A 65.7-kg person stands on the platform at a distance of 1.07 m from the center and a 27.3-kg dog sits on the platform near the person, 1.31 m from the center. Find the moment of inertia of this system, consisting of the platform and its population, with respect to the axis.

Vector A has magnitude of 13.5 and is 345o counter-clockwise up from the +x-axis.  What are the x- and y-components of the vector?

Dr. Evil and his henchmen intend to deflect the Moon from its orbit around Earth by pulling it with a force of 3130 N. They plan to accomplish this by placing a mini black hole 6.17 x 106 m from the center of the Moon and letting gravitation do what gravitation does. What must the mass of the mini black hole be for the evil scheme to succeed? The mass of the Moon is 7.36 × 1022kg.  G = 6.673 x 10-11 N m2/kg2

One mile is equal to 1.609 km.  What is 30.0 mph in m/s?