Explore BrainMass


Mechanics: Collision, Friction, Work, Energy

See attached diagram. A movie stuntman (mass = 80.0 kg) stands on a window ledge 5.0 m above the floor (see figure below.) Grabbing a rope attached to a chandelier, he swings down to grapple with the movie's villain (mass = 70.0 kg) who is standing directly under the chandelier. (Assume that the stuntman's center of mass mov

Work and Energy: Motion on a Skateboard

See attached diagram. Your cousin Throckmorton skateboards down a curved playground ram. Treating Throcky and his skateboard as a particle, his center of mass moves through a quarter-circle with a radius R = 3.0 m (see figure below.) The total mass of Throcky and his skateboard is 25.0 kg. He starts from rest and there is

Linear momentum, bullet's energy, and billiard ball rebound

For the following problems, the answers are given. Show the workings to arrive at the correct answers. 1. If a 60 kg woman is riding in a car travelling at 90km/h, what is her linear momentum relative to (a) The ground (b) the car? Answer: (a) 1.5 x 10^3 kg.m/s (b) zero 2. A 5-g bullet with a speed of 200m/s is fired ho

Beam Balance: Principle of Lever

1) Let's say you are holding a bag of potatoes that you want to buy. The seller tells you that it will cost $0.34 per lb. He then tells you that it weighs 10.0 pounds. You really want these potatoes; there are no potato sellers within miles and you are tired. You have a problem; you don't trust this guy selling the potat

Questions on Classical Mechanics

1. You are loading a spring loaded dart gun and do an amount of work W such that the spring is only 1/3 compressed. How much additional work must you do to fully compress it from 1/3 to fully compressed? Answer in terms of W. 2. A large man tosses a small child onto a large pile of leaves. During the toss, the man exerts ___

Physics for Bicyclists in Tour de France

Bicyclists in the Tour de France do enormous amounts of work during a race. For example, the average power per kilogram generated by Lance Armstrong (m= 75.0 kg) is 6.50 W per kilogram of his body mass. A) How much work does he do during a 135-km race in which his average body speed is 12.0m/s B) Often the work done is e

Determining Amount of Work in Joules: Outer Space Example

(a) Determine the amount of work (in joules) that must be done on a 101 kg payload to elevate it to a height of 1005 km above the Earth's surface. _____ MJ (b) Determine the amount of additional work that is required to put the payload into circular orbit at this elevation. _____ J

A gravitational force case is illustrated.

A pendulum swings left to right. At what locations in the pendulum's swing is the gravitational force doing positive work? Negative work? No work? What is happening to the speed of the pendulum in each case? Where does the pendulum have the greatest gravitational potential energy? Where does it have the greatest kinetic ener

Four questions on mechanics

1. A person standing on the floor is leaning against a wall. The wall exerts on the person a force of 100 N in the horizontal direction. What other horizontal force keeps the person in equilibrium? 2. Torque is measured in Newton meters. Work can also be measured in Newton meters. What are the quantities measured in m

Momentum is explained.

If any conversions are done kg has to be to N or lbs to N and units after answers. 1.) What is linear momemtum of a 198 kg aircraft going 48.3m/s 2.)a 240kg cart runs into the rear of a 134kg cart that is stationary the two carts lock together after the collision and move with a speed of 13.8m/s what is the speed of the

Physics - Simple Machines (Levers)

Levers, pulleys, and wedges are simple machines. Does the concept of work explain why we use these machines in our daily lives, how they work, and why they work? Explain your reasons in two paragraphs, taking examples from daily life.

Physics - Quantum Mechanics - Photons

Please help with the following problems. (1) Suppose that a photon has energy of 5 x 10 -19 J. (five times ten to the negative 19th Joule) What's the wavelength of this photon? What is its frequency? (2) The photon in the above problem strikes a metal plate that has a work function of PHI = 3 x 10 ^ -19 J. What's the max

Physics - Work-Energy Theorem.

A .010-kg bullet traveling horizontally at 400.0 m/s strikes a 4.0-kg block of wood sitting at the edge of a table. The bullet is lodged into the wood. If the table height is 1.2 m, how far from the table does the block hit the floor?

Physics - Work-Energy Theorem..

A 700kg glider is flying in straight and level flight at 90 m/s. What is the initial kinetic energy of the glider and if the pilot decides to trade airspeed for altitude how much alitude can the pilot gain while slowing the glider to 25 m/s? (Neglect loss of energy due to air friction)

Force, work & energy

1) The motor of a ski boat generates an average power of 35900 W when the boat is moving at a constant speed of 17.7 m/s. When the boat is pulling a skier at the same speed, the engine must generate an average power of 80700 W. What is the tension in the tow rope that is pulling the skier? 2) The drawing shows the force-versu

Rotational Speed of a Uniform Disk

A uniform disk with a mass of 895 g and radius 17.0 cm is rotating on frictionless bearings with a rotational speed of 18.0 Hz when Jill drops a 120 g clod of clay on a point 7.90 cm from the center of the disk, where it sticks. What is the new rotational speed of the disk? I was given the equation w=2(pi)F?

a child slides down a hill

A hill has a height h. A child on a sled (total mass m) slides down starting from rest at the top. Does the velocity at the bottom depend on the angle of the hill if: a) It is icy and there is no friction? b) There is friction (deep snow)?

Forces that saved a paratrooper's life

A paratrooper pilot fell 360 m after jumping without his parachute opening. He landed in a snowbank, creating a crater 1.5 m deep, but survived with only minor injuries. Assume the pilot's mass was 80 kg and his terminal velocity was 50 m/s. (a) Estimate the work done by the snow in bringing him to the rest. (in J) (b) Estim

Calculate the force exerted by the man

A 255 kg piano slides 4.4 m down a 30° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. a. Calculate the force exerted by the man. b. Calculate the work done by the man on the piano. c. Calculate the work done by the

Dispersive Waves: Group and Phase Velocity Example Problem

Please see the attached file. In some media, waves of different frequencies travel at different speeds. Such a medium is called a dispersive medium because waves that are not sinusoidal will change shape or disperse over time. For example, a superposition of two such waves of different frequencies is described by the e

Motion of Particle

A particle of mass m moves under a force F = -c(x^3), where c is a positive constant. Find the potential energy function. If the particle starts from rest at x = -a, what is its velocity when it reaches x = 0? Where in the subsequent motion does it instantaneously come to rest? Answer:V=1/4(cx^4); [Sqrt. (c/2m)](a^2); x = +-a

Laws of motion and force on cords

Three blocks are connected on the table as shown below. The table is rough and has a coefficient of kinetic friction of 0.500. The objects have masses of 4.00 kg, 1.00 kg and 2.00 kg, as shown, and the pulleys are frictionless. Determine the acceleration of each object and their directions in terms of up, down, left and, ri

Coefficient of kinetic friction, incline

A child slides down a slide with a 30 degree incline, and at the bottom her speed is precisely half what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child. Police lieutenants, examining the scene of an accident involving two cars, measure the

tensions in the strings and accelerations of the object

Please see the attached file. An object of mass m1 on a frictionless horizontal table is connected to an object of mass m2 through a very light pulley P1 and a light fixed pulley P2 as shown below. (a) If a1 and a2 are the accelerations of m1 and m2, respectively, what is the relation between these accelerations? (

Laws of Motion and Force: Application of Newton's Law

Please see the attached file for full description and diagram. Two objects are connected by a light string that passes over a friction-less pulley. The incline is friction-less, m1 = 2.00 kg, m2 = 6.00 kg, and theta = 55.0 degrees. Answer the following and show all work. Find: a) the acceleration of the objects b) the te

Balancing forces equilibrium

An iron bolt of mass 50.0 g hangs from a string 38.0 cm long. The top end of the string is fixed. Without touching it, a magnet attracts the bolt so that it remains stationary, displaced horizontally 26.0 cm to the right from the previously vertical line of the string. (a) Find the tension in the string. (b) Find the magne

3 good questions in mechanics: Force, work and energy.

Please see the attached file for full problem description. 1.) To immobilize a fractured femur, doctors often utilize the Russell traction system illustrated in the figure below. Notice that one force is applied directly to the knee, F1, while two other forces, F2 and F3, are applied to the foot. The latter two forces combine

Simple Machines: Force required to push a box up a ramp.

1. A 400-lb piano on frictionless casters is to be pushed up a 20 ft ramp to a loading platform 3 ft above the ground. How much force is needed? 2. A block weighing 250 lbs is to be raised into a wagon 30 in high by a boy who can only exert a force of 50 lbs. (a) what is the shortest board he must use as an inclined plane wh

Projectile motion

In a local bar, a customer slides an empty beer mug down the counter for a refill. The bartender is momentarily distracted and does not see the mug, which slides off the counter and strikes the floor at distance d from the base of the counter. The height of the counter is h. (a) With what speed did the mug leave the counter?