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Newtons Laws of motion: Friction

Q- A car is traveling at 50.0 mi/hr on a horizontal highway.
(a) If the coefficient of static friction between road and tires on a rainy day is 0.100, what is the minimum distance in which the car will stop?
(b)What is the stopping distance when the surface is dry and the coefficient of friction is …

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Variable Force

Q- Consider an object on which the net force is a resistive force proportional to the square of its velocity as F = -kmv2, where k is a constant and m is mass of the object. At t = 0 the speed of the object is Vo. Find an expression for the speed of the object at subsequent time t.

Solution:

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Conservation of Momentum

Q- A 65.0 kg boy and his 40.0 kg sister, both wearing roller blades, face each other at rest. The girl pushes the boy hard, sending him backward with a velocity 2.90 m/s toward the west. Ignore friction.

(a) Describe the subsequent motion of the girl.

(b) How much chemical energy is converted in…

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Friction

(On request - Emily)

Q- A 225 kilogram piano is pushed across the floor with a 155 Newton Force if the piano accelerates at 0.37 m/s2 what is the coefficient of friction between the piano and the floor?

Solution:

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Newtons Laws of motion: Friction

Q- An 80 N crate of apples sits at rest on a ramp that runs from the ground to the bed of a truck. The ramp is inclined at 30° to the ground.

(a) What is the normal force exerted on the crate by the ramp?

(b) What is the static frictional force exerted on the crate by the ramp?

(c) What is the m…

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Newtons Laws of motion

(On request)

Q- Two masses m1 = 8.00 kg and m2 = 12.0 kg, connected be a massless string are placed on a triangular wedge of inclines θ1, and θ2 as in the figure. (friction is negligible)

(a) Find the acceleration of the masses.

(b) Find tension in the string.

Solution:

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Newtons Laws of motion: Variable mass

Q- A boat of mass 250kg is coasting, with its engine in neutral, through the water at speed 3.00m/s when it starts to rain. The rain is falling vertically, and it accumulates in the boat at the rate of 10.0 kg/hr.What is the speed of the boat after time 2.00hr has passed? Assume that the water is st…

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Friction

Q- A block of weight 125 N is placed on a horizontal surface and subjected to a force of 75 N as shown in the figure.

(a) If the block remains stationary, find the force of friction acting on the block.

(b) If the block is at the verge of sliding find the coefficient of static friction.

Solutio…

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NLM: Forces

Q- A 40.0 kg crate is suspended between the floor and the ceiling using two spring scales, one attached to the ceiling and one to the floor. If the lower scale reads 117N, what is the reading of the upper scale? Ignore the Weight of the scales.

Solution:

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Newtons Laws of motion: Equilibrium

Q- A 2.0 kg ball tied to a string fixed to the ceiling is pulled to one side by a force F to an angle of 37 degrees from the ceiling.

a) Just before the ball is released and allowed to swing back and forth, how large is the force F that is holding the ball in position.

b) Just before the ball is r…

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Falling Under Air Drag

Q- A skydiver of mass 80.0 kg jumps from a slow-moving aircraft and reaches a terminal speed of 50.0 m/s

  1. What is the acceleration of the skydiver when her speed is 30.0 m/s2?  
  2. What is the drag force on the skydiver when her speed is 50.0 m/s?
  3. What is the drag force on the skydiver when her s…

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Stable Equilibrium

Q- A uniform rod of mass M and length l can rotate freely in a vertical plane about a smooth hinge at one end. A light inextensible string attached to the other end of the rod passes over a smooth peg which is at a height h (greater than l) vertically above the hinge and supports a mass m hanging fr…

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NLM

Q- A ball is tied to the end of an ideal small spring and when it hangs freely at rest, it is found to stretch the spring by 8cm. The ball is now attached to a long string and whirled around in a vertical circle at a constant angular speed. Determine the difference between the maximum amount that th…

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Collision

Q- A block of mass m1 = 4kg moves to the right with a speed of v1 = 10m/s toward a second block of mass m2 = 5kg that moves to the left with a speed v2 =3m/s. after the blocks collide head on; it is found that the m1 remains stationary. Determine the coefficient of restitution between the two blocks…

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Mechanics-NLM

Q- A 6.5 m ladder AB of mass 10 kg leans against a wall as shown. Determine the smallest value of coefficient of static friction between the surfaces (considering same everywhere) for which equilibrium can be maintained.

Solution:

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Friction

Q- A 7gram bullet moves horizontally at 1000m/s toward a 5 kg block that is at rest on a horizontal tabletop. The bullet emerges from the block moving to the right at 400m/s. Determine how far the block will slide if the coefficient of kinetic friction between the block and the table is 0.3, assumin…

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Conical Pendulum

Q- A small bob of mass m is suspended by a string of length l. the bob is moving in a horizontal circle, with constant speed, such that the string makes an angle θ with the vertical. Find:

a) Speed of the bob

b) Angular momentum and

c) work done to bring it to rest.

Solution:

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NLM

Q- A rubber band of spring constant K is wrapped (without tension) around a metal rod of diameter D. The rod is then accelerated upward with an acceleration 100g. What will be the gap between the metal rod and the rubber band at the bottom now? Mass per unit length of the rubber band is m.

Solution…

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Friction

Q- A small coin is placed on the horizontal surface of a rotating disk at a distance r from the center. The disk starts from rest and is given a constant angular acceleration α. The coefficient of static friction between the coin and the disk is µs. Determine the number of revolution N through the…

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Friction-NLM

On request - Kamal

Q- A truck weighing 1 tonne rests on a slope of 30 degrees with its brakes locked. Due to rain the coefficient of friction between the tires and road reduces to 0.3 and the truck starts sliding down the slop under its own weight. What is the net acceleration of the truck down the…

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