Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
Worksheet #15
Supplemental Instruction
Iowa State University
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Course:
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Wesley
PHYS 221
Canfield
10/09/2013
1. (Momentum and Impulse) Bone will rupture if it is subjected to a force density of f.
Suppose a person of mass m carelessly rollerblades into an overhead metal beam that hits
his forehead and completely stops his forward motion. If the area of contact with the
person forehead is A, what is the greatest speed with which he can hit the wall without
breaking any bone if his head is in contact with the beam for a time t?
f = 1.03 X 108 N/m2
m = 70.0 kg
A = 1.5 cm2
t = 10.0 ms
v1 = 2.21 m/s
2. (Conservation of Momentum) Two masses, one of m1 the other of m2 are pressed against
opposite ends of a spring with spring constant k. The spring is compressed by a distance
x. Find the speed of each mass when it has moved free of the spring on a frictionless
horizontal table.
m1 = 1.50 kg
m2 = 1.00 kg
k = 1.75 N/cm
x = 20.0 cm
v1 = 1.25 m/s
v2 = 1.87 m/s
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Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
3. (Conservation of Momentum) In space, an astronaut of mass m1 is attempting to figure
out the mass of a large canister. When it approaches her at v2,i, she pushes against it, to
slow it down to v2,f, but does not reverse it. This action gives her a speed of v1,f. What is
the mass of the canister?
m1 = 78.4 kg
v2,i = 3.50 m/s
v2,f = 1.20 m/s
v1,f = 2.40 m/s
m2 = 81.8