Question

When an object, of mass m, isplacedundertheinfluence of gravitational force of earth (aconservative force) andsomework is done upon theobject by an external force, there will be a change inthe total mechanical energy of the object. If only internal forces are doing work, there is no change in total mechanical energy(gravitationalforce between the mass and the earth are internal forces); it is said to be conserved. Thus, according to work energy theorem:Initial Mechanical Energy + Work done by external forces(work doneby against conservative force)= Final Mechanical EnergyThe work done by external forces can be a positive or a negative work. Whether the work is positive or negative, depends upon the angle between the force and the direction of motion.
Questions –1.A trolley runs from P to Q along a track. At Q its potentialenergy is 50 kJ less thanatP. At P, the kinetic energy of the trolley is 5 kJ. Between P and Q the work the trolley does against friction is 10 kJ. What is the kinetic energy of the trolley at Q?a)35 kJb)45 kJc)55 kJd)65 kJ2.
A car driver adjusts the pressure on a car’s brakes so that the car travels atconstant speed down a hill from P to Q. The magnitude of the change in the car’s kinetic energy is ∆Ek. The magnitude of the change in its gravitational potential energyis∆Ep. Which statement is correct when the car reaches Q?
2a)∆Ek>∆Epb)∆Ek=∆Epc)∆Ep > ∆Ek>0d)∆Ek=
03.An object weighing 10 N is dropped from a height of 4 meters above the ground. When it has fallen freely through a distance of 1 meter, its total mechanicalenergy with respect to the groundisa)2.5 Jb)10 Jc)30 Jd)40 JUse the following diagram to answer question 4 and 5:4.The object will have a minimum gravitational potential energy atwhich of the following point(s)?a)Ab)Bc)Cd)D and E5.The object's kinetic energy at point C is less than its kinetic energy atwhich of the following point(s)?a)A onlyb)A, D and Ec)B onlyd)D and

Answer 1

isplacedundertheinfluence of gravitational force of earth (aconservative force) andsomework is done upon theobject by an external force, there will be a change inthe total mechanical energy of the object. If only internal forces are doing work, there is no change in total mechanical energy(gravitationalforce between the mass and the earth are internal forces); it is said to be conserved. Thus, according to work energy theorem:Initial Mechanical Energy + Work done by external forces(work doneby against conservative force)= Final Mechanical EnergyThe work done by external forces can be a positive or a negative work. Whether the work is positive or negative, depends upon the angle

Answer 2

Answer:

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