Exam 9: Work and Kinetic Energy

Block A (0.40 kg)and block B (0.30 kg)are on a frictionless table (see figure).Spring 1 connects block A to a frictionless peg at 0 and spring 2 connects block A and block B.When the blocks are in uniform circular motion about 0,the springs have lengths of 0.60 m and 0.40 m,as shown.The springs are ideal and massless,and the linear speed of block B is 2.0 m/s.If the distance that spring 2 stretches is 0.060 m,the spring constant of spring 2 is closest to

In the figure,two identical ideal massless springs have unstretched lengths of 0.25 m and spring constants of 700 N/m.The springs are attached to a small cube and stretched to a length L of 0.30 m as in Figure A.An external force P pulls the cube a distance D = 0.020 m to the right and holds it there.(See Figure B.)The external force P,that holds the cube in place in Figure B,is closest to

The work performed as a function of time for a process is given by where What is the instantaneous power output at

The coefficient of the restitution of an object is defined as the ratio of its outgoing to incoming speed when the object collides with a rigid surface.For an object with a coefficient of 0.78,what fraction of the object's kinetic energy is lost during a single collision?

A crane lifts a 425 kg steel beam vertically a distance of How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s²? Neglect frictional forces.

A 4.00-kg mass is attached to a very light ideal spring hanging vertically and hangs at rest in the equilibrium position.The spring constant of the spring is 1.00 N/cm.The mass is pulled downward 2.00 cm and released.What is the speed of the mass when it is 1.00 cm above the point from which it was released?

If electricity costs 6.00¢/kWh (kilowatt-hour),how much would it cost you to run a 120 W stereo system 4.0 hours per day for 4.0 weeks?

An object attached to an ideal massless spring is pulled across a frictionless surface.If the spring constant is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at what is the mass of the object?

If = 3 - + 4 and = x + - 5 ,find x so will be perpendicular to .

A 5.00-kg box slides 4.00 m across the floor before coming to rest.What is the coefficient of kinetic friction between the floor and the box if the box had an initial speed of 3.00 m/s?

If the dot product of two nonzero vectors is zero,the vectors must be perpendicular to each other.

An airplane flies 120 km at a constant altitude in a direction 30.0° north of east.A wind is blowing that results in a net horizontal force on the plane due to the air of 2.40 kN in a direction 10.0° south of west.How much work is done on the plane by the air?

How much energy is needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

A ball is thrown upward at an angle with a speed and direction such that it reaches a maximum height of 16.0 m above the point it was released,with no appreciable air resistance.At its maximum height it has a speed of 18.0 m/s.With what speed was the ball released?

How long will it take a 7.08 hp motor to lift a 250 kg beam directly upward at constant velocity from the ground to a height of 45.0 m? Assume frictional forces are negligible.(1 hp = 746 W)

You carry a 7.0 kg bag of groceries above the level floor at a constant velocity of 75 cm/s across a room that is room.How much work do you do on the bag in the process?

A stock person at the local grocery store has a job consisting of the following five segments: (1)picking up boxes of tomatoes from the stockroom floor (2)accelerating to a comfortable speed (3)carrying the boxes to the tomato display at constant speed (4)decelerating to a stop (5)lowering the boxes slowly to the floor. During which of the five segments of the job does the stock person do positive work on the boxes?

In the figure,two identical springs have unstretched lengths of 0.25 m and spring constants of 300 N/m.The springs are attached to a small cube and stretched to a length L of 0.36 m as in Figure A.An external force P pulls the cube a distance D = 0.020 m to the right and holds it there.(See Figure B.)The work done by the external force P in pulling the cube 0.020 m is closest to

In the figure,two boxes,each of mass 24 kg,are at rest and connected as shown.The coefficient of kinetic friction between the inclined surface and the box is 0.31.Find the speed of the boxes just after they have moved 1.6 m.

A 1000 kg car experiences a net force of 9500 N while decelerating from 30.0 m/s to 23.4 m/s.How far does it travel while slowing down?