Download Quiz 03-1 Forces

AP Physics B
Name__________________
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Mrs. Tsarevsky
Forces
Quiz 3-1
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Problem 1.
A helicopter holding a 70-kilogram package suspended from a rope 5.0 meters long
accelerates upward at a rate of 5.2 m/s2. Neglect air resistance on the package.
a) Draw and label all of the forces acting on the package.
b) Determine the tension in the rope.
c) When the upward velocity of the helicopter is 30 m/s, the rope is cut and the helicopter
continues to accelerate upward at 5.2 m/s2. Determine the distance between the helicopter
and the package 2.0 sec after the rope is cut.
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Problem 2.
Three blocks of masses 1.0, 2.0, and 4.0 kilograms are connected by massless strings, one
of which passes over a frictionless pulley of negligible mass, as shown above. Calculate
each of the following.
a) The acceleration of 4-kiloglam block.
b) The tension in the string supporting the 4-kilogram block.
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c) The tension in the string connected to the 1-kilogram block.
Problem 3.
4 kg
4 kg
2 kg
2 kg
A 10-kg block rests initially on a table as shown in cases I and II above. The coefficient
of sliding friction between the block and the table is 0.2. The block is connected to a cord
of a negligible mass, which hangs over a massless, frictionless pulley. In case I a force of
50 Newtons is applied to the cord. In case II an object of mass 5 kilograms is hung on the
bottom of the cord. Use g = 10 m/s2.
a) Draw a free-body diagram for case I.
b) Calculate the acceleration of the 10-kilogram block in case I.
c) Draw a free-body diagram for case II.
d) Calculate the acceleration of the 10-kilogram block in case II.
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Problem 4
While moving in, a new homeowner is pushing a 20 kg box across the floor at a
constant velocity. The pushing force 120 Newtons is directed downward at an angle 20 to
the horizontal.
a) Draw a free-body diagram.
b) Find the normal force acting on the box.
c) Find force of friction.
d) Find coefficient of kinetic friction between the box and the floor.
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Problem 5.
A block (mass m1) lying on an inclined plane, is connected to a mass m2 by a massless
cord passing over a pulley. The coefficient of kinetic friction between m1 and the plane is
μk, the plane is inclined at an angle θ. As the mass m2 moves down determine the
magnitude of the acceleration of the system in terms of m1, m2, θ, μ, and g.
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Many new cars are equipped with antilock brakes that prevent tires from sliding on
slippery roads during sudden stops. A Honda Accord is traveling at a speed of 17.9 m/s
(about 40 mi/h) on a snow-packed road when the driver applies the brakes. The effective
coefficient of static friction with and without antilock brakes is 0.764 and 0.615,
respectively.
How much less is the stopping distance with antilock brakes than without antilock
brakes?
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