sample-mid-term-2

sample-mid-term-2 - frictionless surface and into a spring....

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Name : ; Signature : ID # : Physics 6A – Winter 2007 – Huang Mid-Term # 2 1. This is a closed book and closed note exam. Students are allowed to bring one page (could be double-sided) note of their own hand- writting. 2. This is a 50 minute exam. No student will be admitted 20 minutes after the start of the exam. 3. This exam counts 20 points towards the Fnal grade. 1 2 3 4 TOTAL
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Problem 1 (5 points) You want to lift a heavy box with a mass of 98.0 kg using a two- pulley system as shown in the Figure. With what minimum force do you have to pull down on the rope in order to lift the box slowly at a constant velocity? If you lift the box by 1.0 m, how much work is done by the gravity and how much work is done by you?
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Problem 2 (5 points) A pendulum bob of mass m is attached to a massless string of length L . If the bob is released from rest at a horizonal position, what is the speed of the bob when the string makes an angle θ with respect to the vertical direction? What is the tension in the string? What is the tangential acceleration of the bob at the angle θ ?
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Problem 3 (5 points) A 1.0-kg block is released from rest and allowed to slide down a
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Unformatted text preview: frictionless surface and into a spring. The far end of the spring is attached to a wall, as shown in the Figure. The initial height of the block is 0.5 m above the lowest part of the slide and the spring constant is 400 N/m. a) What is the speed of the block when it rst reaches the horizontal section of the slide? b) How far is the spring compressed? c) The spring sends the block back to the left. How high does the block rise? Problem 4 (5 points) Starting with an initial speed of 5.00 m/s at a height of 0.300 m, a 1.50-kg ball swings downward and strikes a 4.60-kg ball that is at rest, as the Figure shows. a) Find the speed of the 1.50-kg ball just before impact; b) Assuming that the collision is perfetly inelastic (two balls stick together), nd the speed of the two balls after the collision; c) Find the height from the lowest point that the two ball system will swing up to after the collision, ignoring air resistance....
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sample-mid-term-2 - frictionless surface and into a spring....

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