Explore BrainMass
Share

# Work

### Work at Lifting and Lowering Phase

A weight lifter is bench-pressing a barbell whose mass is 85 kg. He raises the barbell a distance of 0.65m above his chest and then lowers the barbell the same distance. The weight is raised and lowered at a constant velocity. Determine the work done by the weight lifter during (a) the lifting phase and (b) the lowering phase.

### Power Output of a Motor

The crate has a mass of 150 kg and rests on a surface for which the coefficients of static and kinetic friction are us= 0.3 and uk = 0.2 respectively. If the motor supplies a cable force of F = (8t^2 + 20) N, where t is in seconds, determine the power output developed by the motor when t= 5s.

### Kinetic Energy and Work

A 6.0 kg block is pushed 8.0 m up a rough 37 degree inclined plane by a horizontal force of 75N. If the initial speed of the block is 2.2m/s up the plane and a constant kinetic friction force of 25N opposes the motion, calculate the initial kinetic energy of the block, the work done by the 75N force, the work done by the frictio

### Basic Physics Problems (Force; Acceleration; Friction; Energy: Kinetic, Mechanical, Potential)

I would like for you to show me all of your work/calculations and the correct answer to each problem. 38. In an emergency stop to avoid an accident, a shoulder-strap seat belt holds a 60-kg passenger firmly in place. If the car were initially traveling at 90 km/h and came to a stop in 5.5 s along a straight, level road, what

### Average Power P_avg Created by Force F

A sled of mass m is being pulled horizontally by a constant upward force of magnitude F that makes an angle theta with the direction of motion. The coefficient of kinetic friction is mu_k. The average velocity of the sled is v_avg. Find the average power P_avg created by force F. Express your answer in terms of F, theta, a

### Work, Power and Force.

Please do not put your response in a .pdf format, but Word documents are okay. Thanks! (A) A sled of mass m is being pulled horizontally by a constant horizontal force of magnitude F. The coefficient of kinetic friction is mu_k. During time interval t, the sled moves a distance s, starting from rest. Find the average power Pa

### What is the total work done by the two tugboats on the supertanker?

Two tugboats pull a disabled supertanker. Each tug exerts a constant force of 1.9e10^6 N, one at an angle 12.0 degrees west of north, and the other at an angle 12.0 degrees east of north, as they pull the tanker a distance 0.700 km toward the north. What is the total work done by the two tugboats on the supertanker? Express your

### Physics Calculations: Finding the Length of a Ramp

Question: Truck brakes can fail if they get too hot. In some mountainous areas, ramps of loose gravel are constructed to stop runaway trucks that have lost their brakes. The combination of a slight upward slope and a large coefficient of friction in the gravel brings the truck safely to a halt. Suppose a gravel ramp slopes upwar

### Work done/Energy burnt using weight lifting

2.) Your new exercise machine involves lifting weights a standard height of 52.0 cm. a) How much work do you do if you lift 37.8 kg? (in J) Exercise requires a food input about four times your mechanical work output (in other words, about 25% efficiency). A "food calorie" is actually 1000 standard calories and a standard

### Mechanical Work Formulas

1. You and your roommate are dragging an exercise machine (mass 58.9 kg) down a 73.4 meter long hall, from the stair landing, where (because of union rules) the UPS driver left it, to your dorm room. The coefficient of friction with the floor is u = 0.917. a) The mechanical work you do in the process is how many kJ? b) Ass

### Block on a incline AND energy

A block of weight mg sits on an inclined plane as shown. A force of magnitude F is applied to pull the block up the incline at constant speed. The coefficient of kinetic friction between the plane and the block is Mu. What is the total work done on the block by the force of friction as the block moves a distance L up the

1. An overhead projector with a lens of 35.6-cm focal length is used to throw an image on a screen 1.80 m away. If you consider the lens to be a thin lens, how far is the slide from the lens when the image is in focus? What is the magnification in this setup? Work this problem by ray tracing? 2. Work Problem 1 using the thin-

### Coefficient of Kinetic Friction Between Football Uniforms and Astroturf After a Head-On Collision

Fred (mass 70.0 kg) is running with the football at a speed of 7.10 m/s when he is met head-on by Brutus (mass 130 kg), who is moving at 5.10 m/s. Brutus grabs Fred in a tight grip, and they fall to the ground. How far do they slide? The coefficient of kinetic friction between football uniforms and Astroturf is 0.350. Give answe

### Ups and Downs

(a) A ball is launched with initial speed v from ground level up a frictionless slope. The slope makes an angle theta with the horizontal. Using conservation of energy, find the maximum vertical height hmax to which the ball will climb. Express your answer in terms of v, g, and theta. You may or may not use all of these quantiti

### Example Physics Problems

1. If there is a maximum frictional force between your shoe and the track, does that set a limit on how fast your can start (accelerate) in sprint? Does that mean you cannot have more than a certain acceleration even if your have increduly strong leg muscles? What is done to solve this problem? 2. Explain why friction is impo

### Basic Physics (Tension; Displacement; Force etc.)

A 230kg crate hangs from the end of a rope of length L-12.0m. You push horizontally on the crate with a varying force F to move it distance d=4.00m to the side (see attached picture). (a) what is the magnitude of F when the crate is in this final position? During the crate's displacement, what are (b) the total work done on i

### Kinetics Problems

A skier is pulled by a tow rope up a frictionless ski slope that makes an angel of 12 degree with the horizontal. The rope moves parallel to the slope with a constant speed of 1.0m/s. The force of the rope does 900J of work on the skier as the skier moves a distance of 8.0m up the incline. (a) If the rope moved with a constant s

### Roller Coaster Physics

ROLLER COASTER DESIGN Designing a roler coaster is very tricky. Patrons of theme and amusement parks want to be thrilled , but generally do not want to be injured. Downard accelerations of greater than 10 g cause bodily harm. Negative (i.e upward) accelerations of greater than about 5 g also cause damage ( "red out") The

### Distance Calculations of a Football Field

80. To go to a football stadium from your house, you first drive 1000 m north, then 500 m west, and finally 1500 m south. (a) Relative to your home, the football stadium is (1) north of west, (2) south of east, (3) north of east, or (4) south of west. (b) What is the straight-line distance from your house to the stadium? 8

### Roller Coaster Work Problem

The questions refer to the roller coaster in the diagram (attached). The mass of the roller coaster, including passengers = 500 kg. Assume that friction and drag forces are so small they can be ignored. 1. Measured from "ground level," what is the gravitational potential energy of the roller coaster at the top of the first hi

### Force and potential energy and work

Please give complete solutions. Thanks! A spring-loaded dart gun shoots a dart with a mass of 150 grams. The spring constant of the dart gun is 4000 N/m, and when the dart is placed in the gun, the spring is compressed 15 cm (See attachment for the rest).

### Please, find the anwer and show me how you got it if you can

1>What is the electric potential at a point 0.45 m away from a point charge of a of 2.5mC 2> If 3.75 X 10^-4 J of work are required to move 13.7 microc of charge from one point to another, what is the electric potentail difference the two points. 3> An electron is released from rest in a vacumm between two flat, parallel

### Calculating Mass of a Sphere

1) Grains of fine beach sand are assumed to be spheres of radius 57.5 micro meters. These grains are made of silicon dioxide which has a density of 2600kg/m^3. What is the mass of each grain of sand and answer in kg. Got answer of 2.1 * 10^-9 kg from previous work, but wrong answer. Please step by step help work this o

### Micro-F Capacitor Voltages

Hi. Can someone please check these two answers? (a) seems very low and (b) seems very high to me. A 0.22 micro-F capacitor is charged by a 1.5-V battery. After being charged, the capacitor is connected to a small electric motor. Assuming 100% efficiency, (a) to what height can the motor lift a 5.0-g mass? (b) What initial vol

### Fluids, Pressure and Depth

A patient is to receive an intravenous injection of medication. In order to work properly, the pressure of fluid containing the medication must be 109 kPa at the injection point. (a) If the fluid has a density of 1020 kg/m^3, find the height at which the bag of fluid must be suspended above the patient. Assume that the pressure

### Energy of ejected electrons

A magnesium surface has a work function of 3.68 eV. Electromagnetic waves with a wavelength of 215 nm strike the surface and eject electrons. Find the maximum kinetic energy of the ejected electrons. Express your answer in electron volts.

### Equivalent Resistors

1. A series combination of two resistors, 7.25 (the symbol looks like a set of headphones, sorry that's the best I can do to describe it) and 4.03(headphones symbol), is connected to a 9.00 V battery. A. Calculate the equivalent resistance of the curcuit and the current. B. What is the potential difference

### Gravitational Potential Energy of a two body system gained from a loss of projectile's kinetic energy.

A projectile is given a vertical upward velocity Vo = 10000 m/sec at Earth's surface. Neglect air friction. Find the maximum distance it will achieve above the surface of Earth. Do not consider g to be constant.

### Work kinetic energy

Please see the attachments. Power= mom*ang vel. Please use work kinetic energy concepts.

### Average power of a ski lift to raise 100 passengers 150 m in 60 seconds

A ski lift raises 100 passengers averaging 80 kg in mass to a height of 150 m in 60 seconds. What average power does it output during the 60 seconds?