Physics HW 5 - Homework 5 on chapter 5 PDF

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Homework 5 on chapter 5...

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Problem 1: Consider the 68 kg ice skater being pushed by two others shown in the figure. The coefficient of static friction is μs=0.4 and kinetic is μk=0.02. m = 68 kg F1 = 243 N F2 = 187 N

Part (a) Find the magnitude of Ftot, the total force exerted on her by the others, given that the magnitudes F1 and F2 are 243 N and 187 N, respectively in Newtons.

Part (b) Find the direction of Ftot (in degrees relative to the horizontal), the total force exerted on her by the others, given that the magnitudes F1 and F2 are 243 N and 187 N, respectively.

Ftot =_____________________________________

θ =_______________________________________

Part (c) What is the maximum value of the static friction force, in Newtons, that can act on the skater before she moves?

Part (d) What is her acceleration assuming she is already moving in the direction of Ftot in m/s2?.

a =_____________________________________ Fs,max =___________________________________

Problem 2: Consider an object on an incline where friction is present. The angle between the incline and the horizontal is θ and the coefficient of kinetic friction is μk. Part (a) Find an expression for the acceleration of this object. Treat down the incline as the positive direction.

Part (b) Calculate the acceleration, in meters per second squared, of this object if θ = 32° and μk = 0.35. Treat down the incline as the positive direction.

a = __________________________________________ Problem 3: Consider the 57-kg mountain climber in the figure. Part (a) Find the tension in the rope if the mountain climber remains stationary (in Newtons). Assume that the force is exerted parallel to her legs. Also, assume negligible force exerted by her arms.

T = __________________________________________

Part (b) What is the minimum coefficient of friction between her shoes and the cliff? Normal force is the force that is directed out perpendicularly from the object in which friction is being created

μ = __________________________________________

Problem 4: A 570 g squirrel with a frontal surface area of 0.0132 m2 falls from a 9.5 m tree to the ground. Assume the density of air in this problem is given by 1.21 kg/m3. Part (a) What is its terminal velocity in m/s? (Use a Part (b) What will the velocity (in m/s) of a 56 kg drag coefficient of 0.70 and assume down is person falling that distance, assuming no drag positive) contribution?

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vt =_______________________________________ v2 =______________________________________ Problem 5: Calculate the velocity a spherical rain drop would achieve falling (taking downward as positive) from 5.2 km in the following situations. Part (a) Calculate the velocity in the absence of air drag in m/s.

Part (b) Calculate the velocity with air drag in m/s. Take the size across of the drop to be 3.2 mm, the density of air to be 1.22 kg/m3, the density of water to be 1000 kg/m3, the surface area to be πr2, and the drag coefficient to be 1.0.

vt = __________________________________________ Problem 6: TV broadcast antennas are the tallest artificial structures on Earth. In 1987, a 73.5 kg physicist placed himself and 400 kg of equipment at the top of one 610-m high antenna to perform gravity experiments. By how much was the antenna compressed in mm, if we consider it to be equivalent to a steel cylinder 0.150 m in radius? The Young's modulus of steel is 2.10 × 1011 N/m2.

ΔL = __________________________________________

Problem 7: A 20.0-m tall hollow aluminum flagpole is equivalent in strength to a solid cylinder 4.00 cm in diameter. A strong wind bends the pole much as a horizontal force of 1100 N exerted at the top would. How far to the side does the top of the pole flex in mm? Assume the shear modulus is 2.5x1010 N/m2.

ΔL = __________________________________________ Problem 8: When using a pencil eraser, you exert a downward force of 8.5 N at a distance of 1.9 cm from the hardwood-eraser joint. The pencil has a 2.2 mm radius and is held at an angle of 16° to the horizontal. The shear modulus of wood is 1.00 × 1010 N/m2 and the strain modulus is 1.50 × 1010 N/m2. Part (a) By how much does the wood flex perpendicular to its length in meters?

Δx =______________________________________

Part (b) How much is it compressed lengthwise in meters?

ΔL =_____________________________________

Problem 9: The pole in the figure is a a 90° bend in a power line and is therefore subjected to more shear force than poles in straight parts of the line. The tension in the two wires at the top of the pole is 4.1 × 104 N, and both wires are at an angle of 80° with respect to the pole. The pole is 19 m tall, has a 16.5 cm diameter and can be considered to have half the strength of hardwood (hardwood has a Young's modulus of 1.5×1010 N/m2 and a shear modulus of 1×010 N/m2). Part (a) First ignore the guy wire (Tgw). Calculate the compression of the pole, in millimeters.

ΔL = __________________________________________ Part (b) Still ignoring the guy wire, find how much it bends in mm to the right.

Part (c) Now find the tension in the guy wire used to keep the pole straight if it is attached to the top of the pole at an angle of 30° with the vertical in Newtons. (The guy wire must be in the opposite direction of the bend.)

Δx =______________________________________

Tgw = _____________________________________...