Physics140F02exam2

# Physics140F02exam2 - Physics 140 Fall 2002 Midterm 2 1 You...

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Physics 140 Fall 2002 Midterm 2 1 1. You throw a marble with fixed initial speed of 10 m/s from the top of a bridge into the river below. Air drag on the marble can be ignored. To maximize the marble’s kinetic energy on impact with the water, in which direction should you throw it? a) downward b) upward c) horizontally d) at a 45 degree angle downward e) the kinetic energy on impact doesn’t depend on the angle thrown. 2. (P) A witch bungee jumps off a tower positioned 115m above ground level. She has a mass of 65kg and is attached to a bungee with rest length 70m that acts as an ideal spring with spring constant 140Nm. Assuming she drops straight down off the platform from a standing start, how far does the bungee stretch before momentarily stopping the witch’s downward motion? a) 21.1 m b) 25.6 m c) 28.3 m d) 30.2 m e) 35.6 m Yeehooo!

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Physics 140 Fall 2002 Midterm 2 2 3. (P) A uniform, hemispherical sheet of outer radius R and inner radius R /2 is shown below. Given y =0 at the base of the sheet, what is the y-component of its center of mass? a) 0.386 R b) 0.424 R c) 0.495 R d) 0.544 R e) 0.612 R 4. (P) A warlock testing a rocket broom takes off from a standing start and flies at fixed elevation. The warlock and fueled rocket system start out with mass M i . The rocket fires with exhaust speed u , losing mass at a constant rate R , and we’ll assume air drag is negligible. If the rocket broom is to reach a velocity equal to 0.6 u , what minimum fraction of the initial mass must be devoted to fuel? a) 0.38 b) 0.45 c) 0.50 d) 0.55 e) 0.62 y =0 R
Physics 140 Fall 2002 Midterm 2 3 5. (P) Halloween candy fills a box with mass m that initially lies on an incline a distance b from a spring with spring constant k . The box and incline have coefficient of kinetic friction μ k . The box is released and slides a distance d along the incline, compressing the spring. What expression gives the change in kinetic energy (final - initial) of the box

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## This note was uploaded on 04/06/2008 for the course PHYSICS 140 taught by Professor Evrard during the Fall '07 term at University of Michigan.

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Physics140F02exam2 - Physics 140 Fall 2002 Midterm 2 1 You...

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