Work, power & energy Questions and Answers

You slide a 0.12-kg coffee mug 0.15 m across a table. The force you exert is horizontal and of magnitude 0.10 N. The coefficient of kinetic friction between the mug and the table is 0.05. How much work is done on the mug?

You performed the lab again in hopes that another group member could do better. Use the following information to calculate their power using both W/t and Fv. Mass: 70 kg, Height of Stairs: 4.5m , Time1: 3.82s, Time2: 3.94s, Time3: 3.70s

A 5.9 kg bag is held by a string to the ceiling as shown in the diagram below. A 15 g bullet travelling at 361 m/s strikes the stationary bag. The height of the bag after the collision is 13.5 cm. Assuming there is no friction, determine the speed, in metres per second, of the bag after the collision.

A block of 1.0 kg with speed 1.0 m/s hits a spring placed horizontally, as shown in Figure 7. The spring constant is 1000.0 N/m. (a) Calculate the maximum compression of the spring. (b) How far will the block travel before coming to rest? Assume that the surfaces are frictionless.

Part (b) refers to the figure below. The block then goes up the inclined plane again. After the block travels a distance x, the block leaves the spring. The block continues to go up the inclined plane and the block comes to rest after it travels a distance d past the equilibrium position for the spring. What is the distance d?

A system containing a compressed spring, a rubber ball, Earth and air 10 at one point of time contains a grand total of 1000 J of energy. No work was done on or by the system, but at another time the spring compressed to a maximum amount and the ball is NOT moving. Friction is present. At this new point, how much total energy is in the system? a. 1000 J b. Less than 1000 J c. More than 1000 J d. Not enough information to determine the amount of total energy in the system.

If the change in momentum is negative while mass is constant, then... Initial momentum is greater than final momentum Final momentum is greater than initial momentum Kinetic energy decreases Kinetic energy remains the same Kinetic energy increases Momentum decreases Momentum remains the same Momentum increases Acceleration is negative Acceleration is positive

Suppose that an object moves downward with an increasing speed. In this situation, the object's kinetic energy would its potential energy would and its total mechanical energy would. Enter the three answers in their respective order without any commas or spaces between letters. a. remain the same b. decrease c. increase —

Which statement is always true of an object that has kinetic energy? Select one: a. The object is moving on the ground. b. The object is on the ground. c. The object is at rest. d. The object is moving through the air. e. The object is moving.

For questions 3-5, refer to the following information. You are on roller blades on top of a small hill. Your potential energy is equal to 1,000 joules. The last time you checked your mass was 60.0 kilograms. What is the height of the hill? If you start skating down this hill, your potential energy will be converted to kinetic energy. How much kinetic energy will you have at the bottom of the hill?

Use the steps you used in the last two problems to solve. A 4357-kg roller coaster car starts from rest at the top of a 36.5-m high track. Determine the speed of the car at the top of a loop that is 10.8 m high.

A winch is a device used to lift lobster traps out of the water and onto a lobster boat. The winch applies a force of 300 N to lift a trap a distance of 20 m in 12 s. a. Calculate the work performed by the winch to lift the trap. Show your calculations and include units in your answer. b. Calculate the power supplied by the winch to lift the trap. Show your calculations and include units in your answer. The winch then lifts a second trap. c. Explain how the winch could perform the same amount of work but supply a greater amount of power when lifting the second trap. d. Explain how the winch could supply the same amount of power but perform a different amount of work when lifting the second trap.

An ideal spring is hung vertically in its equilibrium position from a ceiling. When a 3.0 kg mass hangs at rest from it, the spring is extended 8.0 cm from its equilibrium length. A downward external force is now applied to the mass to extend the spring an additional 12.0 cm. While the spring is being extended by the external force, what is the elastic potential energy gained by the spring?

Ben Travlun carries a 149-N suitcase up three flights of stairs (a height of 8.7 m) and then pushes it with a horizontal force of 38.9 N at a constant speed of 0.5 m/s for a horizontal distance of 12.7 meters. How much work does Ben do on his suitcase during this entire motion?

A delivery man carries a 5.0-kg box up a flight of stairs 4.0 m above the ground. How much work was done on the box by the man? Remember that he is countering gravity which acts downward with an acceleration of 9.8 m/s^2. A.) J B.) 20 J C.) 49 J D.) 98 J E.) 196 J

Describe the impact of air resistance on the conservation 2 of total mechanical energy. What type of energy does air resistance use to do work? What type of energy increases in a system due to air resistance? Is this work positive or negative and HOW do you know?

6. A battery converts x J of energy in t seconds. Which of the following has the greatest power? A.) x = 3000 Jt = 5.0 s B.) x = 3000 Jt = 10 s C.) x = 4000 Jt = 7.5 s D.) x = 5000 J t = 5.0 s E.) x = 5000 J t = 10 s

4. Which of the following is true about conservation of energy? OA.) Energy can be created within an isolated system. B.) Energy is conserved when the potential energy of a system is minimized. C.) Potential energy can be transferred to kinetic energy but not the other way. D.) The sum of the potential energy and kinetic energy in an isolated system is zero. E.) The total energy within an isolated system must be the same at all times.

6. A toy train car of mass 1.4 kg is moving forwards with a velocity of 2.8 m/s when it strikes a stationary second toy car of mass 1.0 kg. The two cars are magnetic and stick together in a perfectly inelastic collision. What is the final velocity of the two cars combined?

Suppose that two horizontal forces are acting upon a 0.25 kg block: a 5 N force pulling the block and a 2 N frictional force opposing the motion. The block moves a distance of 1.5 m. What is the work done by the 2 N force?

Our central air conditioner uses 10,000 watts on 240 volts. If we leave the thermostat at 76 degrees it runs an average of 8 hours per day. If we move the thermostat to 82 degrees and it runs 3 hours per day, how much money can we save in the month of July? $.05 Cents per KWH

An alpha particle of 4 atomic mass unit is scattered at an angle of 60° after colliding with an oxygen nucleus of 16 atomic mass unit. on the other hand, the oxygen nucleus recoils at an angle of 45" with speed 1.2x 105 m/s. 3b). Find the initial speed of the alpha particle 3c). Find the final speed of the alpha particle

While playing frisbee, you get it stuck 9 meters above you in a tree. You know that if you hit the frisbee hard enough with the rock, you will dislodge the frisbee. If the 75 gram rock needs to be going 6.0 m/s when it hits the frisbee, how fast do you need to throw the rock? Assume there is no energy lost to thermal during this process. You must include a custom conservation of energy statement for this question for full credit. Show work for credit.

Write a custom energy statement for each question when appropriate: W=Fd P W/At PEg = magh KE = 1/2mv2 1. Fignewton pulls a 500. N sled along a flat snowy path using a rope. He pulls with a force of 34.6 N on the rope. The sled moves 16.0 m in 3.00 s. What is Eignewton's power output? b. Fignewton pulls the sled twice as far in twice the time, what is his power output now? 2. Jewel weighs 580 N and she is sitting on a playground swing seat that hangs 0.40 m above the ground. Nuton pulls the swing back, with Jewel on it, and releases it when the seat is 1.00 m above the ground. Mghi-mghf+1/2mv^2f Mghi=1/2mu^2f a. How fast is Jewel moving when the swing moves through the lowest point? b. If Jewel moves through the lowest point at 2.0 m/s, how much work was done on the swing by friction? (hint: solve for thermal energy)

The largest falls stemming from the Niagara River is the Horseshoe Falls or Canadian Falls. There were 15 attempts to go over the falls between 1901 and 1995. How could the speed at the base of the falls be determined using the conservation of energy theorem (AKE = APE)? (Assume an initial speed of zero) v=√√2mgh v = √/2gh v = (2mgh)2 v= (2gh)²

A tank that is 6 feet deep, with a square bottom with sides 4 feet each, has 3 feet of kerosene that weighs 49.9 lb/ft³ in it. How much work (in ft-lb) will it take to pump the kerosene to the rim of the tank?

A construction worker, 28 feet up on a scaffold, lifts a 4-lb rope hand over hand up to the scaffold to raise a cement block weighing 7 pounds off the ground. (Assume the rope is 28 feet long.) How much work (in ft-lb) is required to pull the rope and the block up to the scaffold?

A little boy is in a treehouse, 18 feet up in a tree. He lifts a 3-lb rope hand over hand up to the treehouse. The rope fully extends from the treehouse down to the ground (18ft long). How much work (in ft-lb) is required to pull the rope to the treehouse?

In a playground, a balloon collides with a much heavier soccer ball. During the collision, which of the following is true? The magnitude of the force exerted by the soccer ball on the balloon is equal to the magnitude of the force exerted by the balloon on the soccer ball. The magnitude of the force exerted by the soccer ball on the balloon is greater than the magnitude of the force exerted by the balloon on the soccer ball. The magnitude of the force exerted by the soccer ball on the balloon is smaller than the magnitude of the force exerted by the balloon on the soccer ball. The question cannot be answered without knowing the speeds at which they collided.

The 2.0 million kW of electricity produced by the power plants accounts for only about 50% of the available energy of the moving water of the Niagara river. What accounts for the "lost" energy?

At any given time, 181 kg of water is falling at 31.6 m/s over the Canadian Falls. Use the conservation of energy theorem to determine how high the Canadian Falls mu water is in free fall with an initial speed of zero) 31 m 100 m 15 m 51 m

In its current orientation, water falls from 30.5m above the turbine and the spinning turbine produces 1.000 kWhr of power Determine the velocity of 3.780 kg of water just before it hits the turbine. (Assume the water is in free fall with an initial speed of zero) 147.5 m/s 12.22 m/s 597.8 m/s O24.45 m/s

At any given time, 181 kg of water is falling at 31.6 m/s over the Canadian Falls. Use the conservation of energy theorem to determine how high the Canadian Fall water is in free fall with an initial speed of zero) 15 m 51 m 100 m 31 m

Determine the velocity of 3.780 kg of water just before it hits the turbine. (Assume the water is in free fall with an initial speed of zero) 147.5 m/s 24.45 m/s 12.22 m/s 597.8 m/s

An object with a mass of 200 g rests on a coiled spring with a spring constant of k=500 N/m. The spring is compressed by 5 cm. a. What is the energy stored in the spring? b. How much energy would the spring give to the object? c. How high will the object reach?

A baby carriage is sitting at the top of a hill that is 41 m high. The carriage with the baby weighs 45 kg. The carriage has what type of energy AND which equation will you use to calculate its energy? Kinetic Energy Equation: KE = mgh Potential Energy Equation: PE = mgh Potential Energy Equation: PE=1/2mv² Kinetic Energy Equation: KE = 1/2mv²

A car is traveling with a velocity of 40 m/s and has a mass of 1120 kg. The car has what type of energy AND which equation will you use to calculate its energy? Potential Energy Equation: PE = mv² Potential Energy Equation: PE = mgh Kinetic Energy Equation: KE mu? Kinetic Energy Equaton: KE = mgh

A rollercoaster of mass 2000 kg starts at rest at the top of an 80 m high hill and begins his journey. Friction is negligible. a. What is the coaster's potential energy at the top of the 80 m hill? b. What is the coaster's kinetic energy at the top of the 80 m hill? c. What is the coaster's potential energy at the top of a 30 m hill? d. What is the coaster's kinetic energy at the top of a 30 m hill? e. What is the coaster's speed at the top of a 30 m hill?

In a truck-loading station at a post office a small 0.2 kg package is released from rest at point A on a track that is one quarter of a circle with radius 1.6 m. a. If 1.372 J of work are done against friction as the package slides down the circular arc from A to B, what is the speed of the package when it reaches point B? b. If the package slides along the horizontal surface and comes to rest at point C, how much work was done by friction between points B & C? c. If the force of friction opposing the packages motion as it moves from point B to point C is 0.588 N, how far does the package slide before coming to rest at point C?

How much gravitational potential energy does a 10 kg book have if it is sitting on a shelf 2 meters above the floor? (the acceleration of gravity is 9.8 m/s²) 196 Joules 20 Joules 98 Joules 1 Joule

A 0.51-kilogram ball is thrown vertically downward from a height of 36 meters above the ground. The initial velocity of the ball is 14 meters per second. Neglect air resistance. (a) What will be the velocity of the ball just before it hits the ground? (b) What is the kinetic energy of the ball just before it hits the ground?

A 0.75kg trolley is attached to a spring as shown in the picture. The trolley is pulled back to extend the spring by 15pm. The spring has a spring constant of 80 N/cm. The trolley is released and is accelerated by the spring. Calculate the maximum speed of the trolley. What assumption are you making?

A bobsled zips down an ice track, starting from rest at the top of a hill with a vertical height of 170 m. Disregarding friction, using the equations below what is the velocity of the bobsled at the bottom of the hill? Type your answer below properly rounded to the tenths place!

In which case is positive work being done? a) An eastward force is applied to an eastward moving soccer ball that is already moving at a constant velocity to increase its speed in that direction. b) A cart moving at a constant velocity of 10 m/s [W] when a 0.5 N [E] force is applied. c) Earth applies a force on the Moon as the Moon travels one complete rotation in orbit around the Earth. d) The work done by air resistance on a ball as the ball, which was initally at rest, falls 3.0 m down towards Earth. e) The work done by air resistance as a baseball is thrown horizontally towards the catcher.

In which case is positive work being done? a) An apple falls from a tree. b) Friction slows a puck sliding along the ice. c) A book sits on a shelf 2 m above the floor. d) A skateboarder glides up an incline. e) None of the above.

A 5.00 kg sack of potatoes is raised to a height of 2.00 m and then thrown at a constant velocity of 2.00 m/s onto a truck. What is the initial kinetic energy of the potatoes? a) 103 J b) 10.0 J c) 5.00 J d) 108 J e) 98.0 J

An air hockey paddle hits a 48 g stationary puck with a force of 12 N. The puck travels 5.0 x 10¹ cm on the frictionless surface while the force is applied to the puck. How much work was done on the puck? a) 0.58 J b) 2.4 x 10-2 J c) None of these options is correct. d) 6.0 J e) 6.0 x 10² J

A 45-g golf ball leaves the tee with a speed of 43 m/s after a golf club strikes it. (a) Determine the work done by the club on the ball. [41.6 J] (b) Determine the magnitude of the average force applied by the club to the ball, assuming that the force is parallel to the motion of the ball and acts over a distance of 2.0 cm. [2080 N]

16. A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0 m above the ground. What is the mass of the box? 5.3 kg 6.7 kg 8.0 kg 8.9 kg

13. A sled is moving along a horizontal surface with a speed of 5.7 m/s. It then slides up a rough hill having a slope of 11° above the horizontal. The coefficient of kinetic friction between the sled and the surface of the hill is 0.26. How far along the surface does the block travel up the incline?