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. : "NLM"

Work Done by Variable Force

Q- The force verses displacement graph for a variable force acting on a particle during some displacement is given bellow (the thick lines)

(a) Calculate the total work done by this force on the particle.

(b) Which well-known physical device could produce the type of force during the first 10 seco…

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Newton's Laws: Friction

Q- A box of mass M placed on a table is connected to a hanging mass m by a string passing over a frictionless pulley as in the figure. If the box has mass of 1 kg, the coefficient of friction between the box and table surface is 0.3 and the box slides on the table at constant speed, what is the weig…

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Collision

Q- A truck was traveling north when, at intersection, collided with a car traveling east. The two vehicles remained joined together after the collision. The skid marks leading from the intersection 20 m at an angle of 30o north of east before stopping. The truck weighed 1200 kg and the car weighed …

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Momentum and Impluse

(a) What is the impulse needed to stop a 20 kg bowling ball moving at 5 m/s?

(b) A 2000 kg car accidentally drops from a crane and crashes at 30 m/s to the ground below and comes to an abrupt halt. What is the momentum at impact?

(c) A railroad diesel engine weighs two times as much as a freight c…

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Friction

(On request - Krupa)

Q- A heavy uniform chain lies on horizontal table top If coefficient of friction between the chain and the table top is 0.25 then what is the maximum fraction of the length of the chain that can hang over the edge of the table? 

Solution:

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Newton's Laws of Motion

Q- A man claims that as long as he has his seat belt on, he can hold on to a 12.0 kg child in a 60.0 mi/h head on collision with a brick wall in which the car passenger compartment comes to a stop in 0.050 s. Is his claim true? Explain why he will experience a violent force during the collision, tea…

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Friction and Projectile

Q- A block slides 6 feet down the incline of an escalator and then it slides for 2 feet along the level portion until if flies off. If the level portion of the escalator is 3 feet above the floor, determine how far from the base of the escalator the block will strike the floor. Assume that the coeff…

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Force and Friction

(On request- William)

Q- is it easier to move a box that is sitting on the ground (a) by pulling the box from a rope that makes an angle of 300 with the surface or(b) by pushing the box with the force that makes the same angle (but pointing downward) with the surface?

Solution:

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NLM: Tension

(On request- William)

Q- A traffic light weighing 122N hangs from a cable tied to two other cables fastened to a support. The upper cables make angles 370 and 530 with the horizontal. Find the tension in the cables.

Solution: 

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Newton's Law: Vectors

Q- Three astronauts, propelled by jet backpacks, push and guide a 195 kg asteroid toward a processing dock. One astronaut exerts a force of 30 N, 300 from positive x-axis towards positive y direction, second exerts a force of 55 N along the x-axis and third astronaut exerts a force of 41 N, 600 from…

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Newton's Law: Variable Mass

Q - A spherical raindrop of radius a, falls from rest under gravity. It falls through a stationary cloud such that because of condensation its radius increases with time at a constant rate k. Find the distance fallen by the raindrop as a function of time t.

Solution:

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Friction

Q- An aluminum block is pushed to the right with and initial speed of v1=10 ft/s at the same time a copper block is pushed to the left with an initial speed of v2=16 ft/s. both blocks slide along a horizontal steel floor toward each other. if the blocks were initially d = 10 ft. apart determine how …

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Impulse and Momentum

Q- (a) What is the impulse needed to stop a 20 kg bowling ball moving at 5 m/s?

(b) A 2000 kg car accidentally drops from a crane and crashes at 30 m/s to the ground below and comes to an abrupt halt. What is the momentum at impact?

(c) A railroad diesel engine weighs two times as much as a freig…

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Motion: Variable Mass

Q- a small body of mass m0 is projected vertically upwards in a cloud. Its initial speed is √(2gk). During its motion the body picks up moisture from the stationary cloud. Its mass at height x above the point of projection is m0(1+ ρx),where ρ is a +ve constant. Show that the greatest height h sa…

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Newton's Laws of Motion

(on request - Shantanu)

Q- A man with mass m=75 kg is standing on a scale in an elevator. Find what the scale shows in the following two situations.
(a) the elevator is going up while speeding up at 2 m/s2
(b) the elevator is going down while slowing down at 2 m/s2

Solution

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Friction

Q- Two blocks of mass m1 = 12.0 kg and m2 = 18.0 kg connected by a rope of negligible mass are being dragged by a horizontal force F=68.0 N acting on m2. The coefficient of kinetic friction between each block and the surface is 0.100 Determine magnitude of acceleration in the blocks and the tension…

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Newton's Laws

Q- An object of mass 5.00 kg, attached to a spring scale, rests on a frictionless, horizontal surface. The spring scale attached to the rear of a boxcar, has constant reading of 18.0 N when the car is in motion.

(a) Determine the acceleration of the car.

(b) What constant reading will the sprin…

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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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