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David goes through some example problems on the concept of work. By reviewing these, you'll have a better knowledge of how to calculate work done by individual forces on an object in motion. You'll also understand the formula definition of work and how forces like tension, friction, and gravity play a role, and be able to apply the work-energy ...
- 5 min
- David SantoPietro
- If the trashcan's velocity is constant, that means it has no net acceleration. If it has no acceleration, there is no net force on the object, sinc...
- Yes, you need slightly more than 39.2N to trigger the initial acceleration.
- static friction applies when there is no movement. Hence, no displacement = no work done.
- Well we assume the body is already in motion.So we ignore the fact that an initial force was applied which was larger than gravitational force and...
- Yes. It means that the force and displacement vectors are opposite. So, lifting a crate up means gravity is doing negative work and you do positive...
- It does not matter. There certainly is no law of physics that says angles must be measured that way.
- Yeah, this is a bad example. He needed to make one of the following conditions: 1) the can starts from rest and ends at rest. In that case you put...
- Good question. The answer is no. It might seem that the laws of physics say yes, because if normal is equal and opposite to mg, then adding a small...
- Well then the work would be calculated like the example given before using KE= 1/2 (mv^2). We would need to know the velocity to calculate the KE (...
- Work Problems: Constant Force
- Work Problems in A Uniform Circular Motion
- Work Problems on An Incline
- Summary
Problem (1): A constant force of 1200 N is required to push a car along a straight line. A person displaces the car by 45 m. How much work is done by the person? Solution: If a constant force FFF acts on an object over a distance of ddd, and FFF is parallel to ddd, then the work done by force FFFis the product of the force times distance. In this c...
Problem (10): A 5-kg object is held at the end of a string and undergoes uniform circular motion around a circle of radius 5 m5\,{\rm m}5m. If the tangential speed of the object around the circle is 15 m/s15\,{\rm m/s}15m/s, how much work was done on the object by the centripetal force? Solution: Here, an object moves around a circle, so we encount...
Problem (11): A 5−kg5-{\rm kg}5−kg box, initially at rest, slides 2.5 m2.5\,{\rm m}2.5m down a ramp of angle 30∘30^\circ30∘. The coefficient of friction between the box and the incline is μk=0.435\mu_k=0.435μk=0.435. Determine (a) the work done by the gravity force, (b) the work done by the frictional force, and (c) the work done by the normal for...
Here, we learned how to calculate the work done by a constant force in physics by solving a couple of example problems. Overall, the work done by a constant force is the product of the horizontal component of the force times the displacement between the initial and final points. In addition, power, a related quantity to work in physics, is also def...
- Renatta Gass is out with her friends. Misfortune occurs and Renatta and her friends find themselves getting a work out. They apply a cumulative force of 1080 N to push the car 218 m to the nearest fuel station.
- Hans Full is pulling on a rope to drag his backpack to school across the ice. He pulls upwards and rightwards with a force of 22.9 Newtons at an angle of 35 degrees above the horizontal to drag his backpack a horizontal distance of 129 meters to the right.
- Lamar Gant, U.S. powerlifting star, became the first man to deadlift five times his own body weight in 1985. Deadlifting involves raising a loaded barbell from the floor to a position above the head with outstretched arms.
- Sheila has just arrived at the airport and is dragging her suitcase to the luggage check-in desk. She pulls on the strap with a force of 190 N at an angle of 35° to the horizontal to displace it 45 m to the desk.
We have 20 ready-to-use problem sets on the topic of Work, Energy, and Power. These problem sets focus on the use of energy principles to mathematically analyze systems involving the motion of objects. Click a link to open a publicly-available problem set.
On the following pages you will find some problems of work and energy with solutions. Try to do them before looking at the solution. Work and Energy - Work done by a constant force. Work and Energy - Work done by the weight force and potential energy.
Let’s consider an example that can help illustrate the differences among work, force, and power. Suppose the woman in Figure 9.3 lifting the TV with a pulley gets the TV to the fourth floor in two minutes, and the man carrying the TV up the stairs takes five minutes to arrive at the same place.
Use this data set and your favorite application for analyzing data to solve the following problems. Use the given data to create a force-displacement graph. Determine the work done on the projectile as a function of its displacement. Compute the launch speed of the projectile.
