HW5Sol - Oregon State University Physics 201 , Fall 2009...

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Unformatted text preview: Oregon State University Physics 201 , Fall 2009 HW5 (due Nov. 2 at 5:00 p.m.) Page 1 Oregon State University Physics 201 Fall Term, 2009 HW5 Solutions 1. A 250-kg projectile is f red From the ground with a speed oF 120 m/s at a 60.0 angle above the horizontal. At the highest point oF its arc, it explodes into three pieces, A, B and C, all oF equal mass. Immediately aFter the explosion, pieces A and B are still moving with the same speed as the whole projectile had right beFore the explosion. However, A is moving vertically down- ward, and B is moving horizontally Forward (i.e. in the same direction as the projectile prior to its explosion). ind the velocity oF C right aFter the explosion. Momentum just before the explosion: Momentum just after the explosion: P i P f ( f = P A + P B + P C ) I. Find the momentum just before the explosion (and its all x-momentum): Use this equation : P i = m total v i Use these knowns: m total = 250 (given) Solve for: P i ( 15,000 kgm/s ) v i = 120 cos(60) ( x-velocity of proj.) II. Find the x momentum of part C just after the explosion: Use this equation : P f.x = P A.x + P B.x + P C.x Use these knowns: P f.x = 15,000 (from step I ) Solve for: P C.x ( x 10,000 kgm/s ) P A.x = 0 (givenA goes downward) P B x = m B v i (givenB continues forward) m B = 250/3 (given) v i = 120 cos(60) ( x-velocity of proj.) III. Find the y momentum of part C just after the explosion: Use this equation : P f.y = P A.y + P B.y + P C.y Use these knowns: P f.y = 0 ( P i = P f was all f x-dir.) Solve for: P C.y ( 5,000 kgm/s ) P A.y = m A v i (givenA goes downward) P B y = 0 (givenB continues forward) m A = 250/3 (given) v i = 120 cos(60) ( x-velocity of proj.) IV. Find part Cs total momentum magnitude just after the explosion: Use this equation : || P C || = ( P C.x 2 + P C.y 2 ) 1/2 Use these knowns: P C.x = 10,000 (from step II ) Solve for: || P C || ( 11,180 kgm/s ) P C.y = 5,000 (from step III ) P A P B P C Oregon State University Physics 201 , Fall 2009 HW5 (due Nov. 2 at 5:00 p.m.) Page 2 V. Find part Cs total momentum direction just after the explosion: Use this equation : || P C || = tan-1 ( P C.y / P C.x ) Use these knowns: P C.x = 10,000 (from step II ) Solve for: C ( 26.6 ) P C.y = 5,000 (from step III ) VI. Find part Cs speed just after the explosion: Use this equation : || P C || = m C || v C || Use these knowns: || P C || = 11,180 (from step IV ) Solve for: || v C || ( 134 m/s ) m C = 250/3 (given) Piece Cs velocity just after the explosion is 134 m/s at an angle of 26.6 above the horizontal. Oregon State University Physics 201 , Fall 2009 HW5 (due Nov. 2 at 5:00 p.m.) Page 3 2. Two pucks collide on a level air-hockey table. Puck A has a mass of 0.0250 kg and is moving initially due eastward at a speed of 5.50 m/s. Puck B has a mass of 0.0500 kg and is initially at rest. Right after the collision, puck A is moving in a direction 65.0 north of east; and puck B is moving in a direction 37 south of east. moving in a direction 37 south of east....
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This note was uploaded on 01/13/2010 for the course PH 201 taught by Professor Staff during the Fall '08 term at Oregon State.

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HW5Sol - Oregon State University Physics 201 , Fall 2009...

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