Ch 07: Newton's Third Law
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Problem 2
A bicycle coasting at 8.0 m/s comes to a 5.0-m-long, 1.0-m-high ramp. What is the bicycle's speed as it leaves the top of the ramp?Problem 2
A car traveling at 30 m/s runs out of gas while traveling up a 10 degree slope. How far up the hill will it coast before starting to roll back down?Problem 2
A skier is gliding along at 3.0 m/s on horizontal, frictionless snow. He suddenly starts down a 10 degree incline. His speed at the bottom is 15 m/s. (a) What is the length of the incline?Problem 2
FIGURE P2.64 shows a fixed vertical disk of radius R. A thin, frictionless rod is attached to the bottom point of the disk and to a point on the edge, making angle Φ (Greek phi) with the vertical. Find an expression for the time it takes a bead to slide from the top end of the rod to the bottom.
Problem 2
A snowboarder glides down a 50-m-long, 15 degree hill. She then glides horizontally for 10 m before reaching a 25 degree upward slope. Assume the snow is frictionless. (b) How far can she travel up the 25 degree slope?Problem 2
A very slippery block of ice slides down a smooth ramp tilted at angle θ. The ice is released from rest at vertical height h above the bottom of the ramp. Find an expression for the speed of the ice at the bottom.Problem 6
A rifle with a barrel length of 60 cm fires a 10 g bullet with a horizontal speed of 400 m/s. The bullet strikes a block of wood and penetrates to a depth of 12 cm. b. How long does it take the bullet to come to rest?Problem 6
Bob is pulling a 30 kg filing cabinet with a force of 200 N, but the filing cabinet refuses to move. The coefficient of static friction between the filing cabinet and the floor is 0.80. What is the magnitude of the friction force on the filing cabinet?Problem 6
A rubber-wheeled 50 kg cart rolls down a 15 degrees concrete incline. What is the magnitude of the cart's acceleration if rolling friction is (a) neglected and (b) included?Problem 6
A 4000 kg truck is parked on a 15 degrees slope. How big is the friction force on the truck? The coefficient of static friction between the tires and the road is 0.90.Problem 6
A 5.0 kg wooden sled is launched up a 25° snow-covered slope with an initial speed of 10 m/s. a. What vertical height does the sled reach above its starting point?Problem 6
A block of mass m is at rest at the origin at t = 0. It is pushed with constant force F₀ from 𝓍 = 0 to 𝓍 = L across a horizontal surface whose coefficient of kinetic friction is μₖ = μ₀ ( 1 - 𝓍/L ) . That is, the coefficient of friction decreases from μ₀ at 𝓍 = 0 to zero at 𝓍 = L. b. Find an expression for the block's speed as it reaches position L.Problem 6
Bonnie and Clyde are sliding a 300 kg bank safe across the floor to their getaway car. The safe slides with a constant speed if Clyde pushes from behind with 385 N of force while Bonnie pulls forward on a rope with 350 N of force. What is the safe's coefficient of kinetic friction on the bank floor?Problem 6
A 1500 kg car skids to a halt on a wet road where mu(k) = 0.50. How fast was the car traveling if it leaves 65-m-long skid marks?Problem 6
A baggage handler drops your 10 kg suitcase onto a conveyor belt running at 2.0 m/s. The materials are such that μₛ = 0.50 and μₖ = 0.30. How far is your suitcase dragged before it is riding smoothly on the belt?Problem 6
Sam, whose mass is 75 kg, takes off across level snow on his jet-powered skis. The skis have a thrust of 200 N and a coefficient of kinetic friction on snow of 0.10. Unfortunately, the skis run out of fuel after only 10 s. a. What is Sam's top speed?Problem 6
The 2.0 kg wood box in FIGURE P6.58 slides down a vertical wood wall while you push on it at a 45° angle. What magnitude of force should you apply to cause the box to slide down at a constant speed?Problem 6
A 50,000 kg locomotive is traveling at 10 m/s when its engine and brakes both fail. How far will the locomotive roll before it comes to a stop? Assume the track is level.Problem 6
A 1.0 kg wood block is pressed against a vertical wood wall by the 12 N force shown in FIGURE P6.57. If the block is initially at rest, will it move upward, move downward, or stay at rest?Problem 6
A large box of mass M is moving on a horizontal surface at speed v₀. A small box of mass m sits on top of the large box. The coefficients of static and kinetic friction between the two boxes are μₛ and μₖ, respectively. Find an expression for the shortest distance dₘᵢₙ in which the large box can stop without the small box slipping.Problem 7
(b) How much force does the astronaut exert on his chair while accelerating straight up at 10 m/s^2?Problem 7
A 1000 kg car is pushing an out-of-gear 2000 kg truck that has a dead battery. When the driver steps on the accelerator, the drive wheels of the car push horizontally against the ground with a force of 4500 N. Rolling friction can be neglected. (a) What is the magnitude of the force of the car on the truck?Problem 7
Blocks with masses of 1 kg, 2 kg, and 3 kg are lined up in a row on a frictionless table. All three are pushed forward by a 12 N force applied to the 1 kg block. (b) How much force does the 2 kg block exert on the 1 kg block?Problem 7
The foot of a 55 kg sprinter is on the ground for 0.25 s while her body accelerates from rest to 2.0 m/s. (b) What is the magnitude of the friction force?Problem 7
A 75 kg archer on ice skates is standing at rest on very smooth ice. He shoots a 450 g arrow horizontally. When released, the arrow reaches a speed of 110 m/s in 0.25 s. Assume that the force of the bow string on the arrow is constant. b. What is the archer's recoil speed?Problem 7
A 2.0-m-long, 500 g rope pulls a 10 kg block of ice across a horizontal, frictionless surface. The block accelerates at 2.0 m/s^2. How much force pulls forward on (b) the rope? Assume that the rope is perfectly horizontal.Problem 7
A rope of length L and mass m is suspended from the ceiling. Find an expression for the tension in the rope at position y, measured upward from the free end of the rope.Problem 7
A house painter uses the chair-and-pulley arrangement of FIGURE P7.45 to lift himself up the side of a house. The painter's mass is 70 kg and the chair's mass is 10 kg. With what force must he pull down on the rope in order to accelerate upward at 0.20 m/s².Problem 7
An 85 kg cheerleader stands on a scale that reads in kg. b. What does the scale read if the 85 kg cheerleader lifts the 50 kg cheerleader upward with an acceleration of 2.0 m/s²?Problem 7
FIGURE EX7.17 shows two 1.0 kg blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at 3.0 m/s^2 by force F. (b) What is the tension at the top end of rope 1?
