6.4 " Suppose the worker in Exercise 6.3 pushes downward at an angle of 30 below the horizontal .(a) What magnitude of force must the worker apply to move the crate at constant velocity ?(b) How much work is done on the crate by this force when the crate is pushed a distance of 4.5 m? (c) How much work is done on the crate by friction during this displacement ? (d) How much work is done on the crate by the normal force ?By gravity ?(e) What is the total work done on the crate? 621 ' You are a member of an Alpine Rescue Team. You must project a box of supplies up an incline of constant slope angle a so that it reaches a stranded skier who is a verh'cal distance ft above the bottom of the incline .The incline is slippery Jbut there is some friction present Jwith kinetic friction coefficient mk. Use the work energy theorem to calculate the minimum speed you must give the box at the bottom of the incline so that it will reach the skier . Express your answer in terms of gJ hJ ka and a. 6.33 Three identical 6.40 -kg masses are hung by three identical springs J as shown in Fig. E6.33 . Each spring has aforce constant of 2.80 kN>m and was 12.0 cm long before any masses were attached to it. (a) Draw a free -body diagram of each mass . (b) How long is each spring when hanging as shown ?(Hint: First isolate only the bottom mass .Then treat the bottom two masses as a system. Finally, treat all three masses as a system.) 6.41r .. CALC A force in the Xdirection with magnitude F1X2 = 18.0 N 10.530 N>m2x is applied to a 6.00 kg box that is sitting on the horizontal J frictionless surface of a frozen lake . F1X2 is the only horizontal force on the box . If the box is initially at rest atx = 0J what is its speed after it has traveled 14.0 m? 6.51 \"Magnetar. On December 2?, 2004 J astronomers observed the greatest flash of light ever recorded from outside the solar system . It came from the highly magnetic neutron star SGR 1806 -20 (a magnetar ). During 0.20 s, this star released as much energy as our sun does in 250000 years .If P is the average power output of our sun J what was the average power output (in terms of?) of this magnetar ? Extra Problem 5: 6.61 .. CALC Rotating Bar.A thin, uniform 12.0kg bar that is 2.00 m long rotates uniformly about apivot at one endJmaking 5.00 complete revolutions every 3.00 seconds .What is the kinetic energy of this bar ? (Hint: Different points in the bar have different speeds .Break the bar up into infinitesimal segments of mass rim and integrate to add up the kinetic energies of all these segments .) 6.65 CD A 20.0kg crate sits at rest at the bottom of a 15.0mlong ramp that is inclined at 34.0 0 above the horizontal . A constant horizontal force of 290 N is applied to the crate to push it up the ramp .While the crate is moving Jthe ramp exerts a constant frictional force on it that has magnitude 65.0 N. (a) What is the total work done on the crate during its motion from the bottom
