EXERCISES & PROBLEMS KINETIC ENERGY AND WORK
ssm Solution is in the Student Solutions Manual.
www Solution is available on the World Wide Web at:
Ilw Solution is available on the Interactive Leaming Ware.
IE. If an electron (mass m = 9.1 1 X 10-31 kg) in copper rear the lowest possible temperature has a kinetic energy of 6.7 X 10-191,what is the speed of the electron?
2E. On August 10, 1972, a large meteorite skipped across. The accompanying fireball was so bright that it could be seen in the daytime.
3E. Calculate the kinetic energies of the following objects moving at the given speeds: (a) a 110 kg football linebacker running the aircraft carrier.
4P. A father racing his son has half the kinetic energy of he son. who has half the mass of the father.
5P. A proton (mass m = 1.67 X 10-27 kg) is being accelerated along a straight line at 3.6 X 101~m/s~ in a machine. If the proton has an initial speed.
6E. A floating ice block is pushed through a displacement straight bank rushing water, which exerts a force on the block.
7E. To pull a 50 kg crate across a horizontal friction less floor, a worker applies a force of 210 N, directed 20· above the horizontal.
8E. A 1.0 kg standard body is at rest on a friction less horizontal air track when a constant horizontal force F acting in the positive.
9E. A luge and its rider, with a total mass of 85 kg, emerges from a downhill track onto a horizontal straight track with an initial speed of 37 m/s. If they stop at a constant deceleration.
lOP. A force acts on a 3.0 kg particle-like object in such a way that the position of the object as a function of time is given by .r = 3.0( – 4.0(2 + 1.0(3. with x in meters and ( in seconds.
11P Shows three forces applied to a trunk that moves leftward by ,3.00 m over a friction less floor.
12P.The only force acting on a 2.0 kg canister that is moving in an plane has a magnitude of 5.0 N. The canister initially has a velocity of 4.0 m in the positive x direction.
13P. Shows an overhead view of three horizontal forces acting on a cargo canister that was initially stationary but that now moves across a friction less floor.
Work Done by a Gravitational Force
14E. (a) In 1975 the roof of Montreal’s Velodrome. with a weight of 360 , was lifted by 10 so that it could be centered. How much work was done on the roof by the forces making the lift? (b) In 1960 Mrs. Maxwell Rogers of Tampa, Florida, reportedly raised .
lSE. In Fig. 7-28. a cord runs around two mass less, friction less pulleys; a canister with mass m = 20 kg hangs from one pulley.
16P. A cord is used to vertically lower an initially stationary block of mass M at a constant downward acceleration . When the block has fallen a distance d, find (a) the work done by the cord’s force on the block, (b) the work done by gravitational force on the block, (c) the kinetic energy of the block, and (d) the speed of the block.
Work Done by a Spring Force
17E. During spring semester at MIT, residents of the parallel buildings of the East Campus dorms battle one another with large catapults that are made with surgical hose mounted on a window frame.
18E. A spring with a spring constant of 15 N/cm has a cage attached . (a) How much work does the spring force do on the cage when the spring is stretched from its relaxed .
19P. A 250 g block is dropped onto a relaxed vertical spring that has a spring constant.
19P. The only force acting on a 2.0 kg body as it moves along the positive x axis has an x component.
Work Done by a General Variable force
20E. A 5.0 kg block moves in a straight line on a horizontal friction less surface under the influence of a force that varies with position.
21P. A force of 5.0 N acts on a 15 kg body initially at rest. Compute the work done by the force in (a) the first, (b) the second, and (c) the third seconds and (d) the- instantaneous power due to the force at the end of the third second.
22P. A skier is pulled by a tow rope up a friction less ski slope that makes an angle of 12° with the horizontal. The rope moves parallel to the slope with a constant speed.
23P. A fully loaded, slow-moving freight elevator has with a total mass of 1200 kg, which is required to travel upward 54 m in 3.0 min, starting and ending at rest.
24P. A 0.30 kg ladle sliding on a horizontal friction less surface is attached to one end of a horizontal spring (with k = 500 N/m) whose other end is fixed.
25P. The force (but not the power) required to tow a boat at constant velocity is proportional to the speed. If a speed.
26P. Boxes are transported from one location 10 another in a warehouse by means of a conveyor belt that moves with a constant speed of 0.50 m/s. At a Certain location the conveyor.
27P. A horse pulls a cart with a force of 40 at an angle of 30° above the horizontal and moves along of a speed of 6.0 mi/h. (a) How much work does the force do in 10 min? (b) What is the average power (in horsepower) of the force.