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Exam 4: The Laws of Motion: Part A

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Question 1

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Superguy is flying at treetop level near Paris when he sees the Eiffel Tower elevator start to fall (the cable snapped) .His x-ray vision tells him Lois LaTour is inside.If Superguy is 1.00 km away from the tower,and the elevator falls from a height of 2.1 × 10² m,how long does Superguy have to save Lois,and what must be his average speed?

A) 4.5 s,200 m/s
B) 6.5 s,150 m/s
C) 7.0 s,140 m/s
D) 9.0 s,110 m/s

E) All of the above
F) B) and C)

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Question 2

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A bridge that was 8.3 m long has been washed out by the rain several days ago.How fast must a car be going to successfully jump the stream? Although the road is level on both sides of the bridge,the road on the far side is 2.0 m lower than the road on this side.

A) 5.0 m/s
B) 7.8 m/s
C) 13 m/s
D) 25 m/s

E) A) and D)
F) All of the above

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Question 3

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A stone is thrown with an initial speed of 15 m/s at an angle of 53° above the horizontal from the top of a 40-m building.If g = 9.8 m/s² and air resistance is negligible,then what is the magnitude of the horizontal component of velocity as the rock strikes the ground?

A 12.0-kg mass is placed on a 25.0° incline and friction keeps it from sliding.The coefficient of static friction in this case is 0.580 and the coefficient of sliding friction is 0.520.The mass is given a shove causing it to slide down the incline.Taking down the incline as positive,what is the acceleration of the mass while it is sliding?

A projectile is fired over a horizontal surface at an angle of elevation of 70°.Neglecting air resistance,what are possible angles in flight between the acceleration vector and the velocity vector?

A projectile is launched with speed v at an angle θ,the angle being less than 45º.What other angle would give the same range for this projectile launched at the same speed v?

A stone is thrown with an initial speed of 15 m/s at an angle of 53° above the horizontal from the top of a 40-m building.If g = 9.8 m/s² and air resistance is negligible,then what is the speed of the rock as it hits the ground?

A 2000-kg sailboat experiences an eastward force of 2000 N by the ocean tide and a wind force against its sails with magnitude of 6000 N directed toward the northwest (45° N of W) .What is the direction of the resultant acceleration?

Dana uses a rope to pull a box that weighs 300 N across a level surface with constant velocity.The rope makes an angle of 30° above the horizontal and the tension in the rope is 50 N.What is the coefficient of friction?

A 500-N tightrope walker stands at the center of the rope.If the rope can withstand a tension of 1400 N without breaking,what is the minimum angle the rope can make with the horizontal?

A 6.0-kg object is falling downward with an acceleration of 3.27 m/s².Of the following values,which is nearest to the drag force on the object?

A solid steel ball is dropped from a great height and when its speed reaches 20 m/s its acceleration downward is 7.35 m/s².What would be the terminal velocity in this situation?

An Olympic skier moving at 22.0 m/s down a 30.0° slope encounters a region of wet snow,of coefficient of friction µ_k = 0.740.How far down the slope does she go before stopping?

A 12.0-kg mass is placed on a 25.0° incline and friction keeps it from sliding.The coefficient of static friction in this case is 0.580,and the coefficient of sliding friction is 0.520.The mass is given a shove causing it to slide down the incline.What is the frictional force while the mass is sliding?

A baseball is moving in the air along the customary parabola.Ignoring air drag,where is the force on the baseball zero?

A sled is on a horizontal surface and a rope with tension T is pulling on it at an angle θ above the horizontal.The sled had mass M and does not move due to the frictional force.In this case the coefficient of friction is μ​_s.In terms of the variables given and g,what is the magnitude of the frictional force in this case?

A plane is moving due north,directly towards its destination.Its airspeed is 200 mph.A constant breeze is blowing from west to east at 40 mph.How long will it take for the plane to travel 200 miles north?

A sphere is dropped from a great height and when its speed reaches 20 m/s,its acceleration downward is 8.4 m/s².If the drag force is proportional to the square of the speed,what will be its acceleration downward when its speed reached 40 m/s?

A stone is thrown at an angle of 30° above the horizontal from the top edge of a cliff with an initial speed of 14 m/s.A stop watch measures the stone's trajectory time from top of cliff to bottom to be 7.1 s.How far out from the cliff's edge does the stone travel horizontally? Note: g = 9.8 m/s² and air resistance is negligible.

A 150-N sled is pulled up a 28° slope at a constant speed by a force of 120 N.What is the coefficient of kinetic friction between sled and slope?