Question about Force and Motion
Several force and motion problems attached.
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1. A 68 kg crate is dragged across a floor by pulling on a rope attached to the crate
and inclined 15 degrees above the horizontal. (a) If the coefficient of static
friction is 0.50, what minimum force magnitude is required from the rope to start
the crate moving ? (b) If the friction is 0.35, what is the magnitude of the initial
acceleration of the crate ?
2. A loaded penguin sled weighing 80 Newton’s rests on a plane at 20 degree’s to
the horizontal. Between the sled and the plane the coefficient of static friction is
0.25 and the coefficient of friction is 0.15. (a) What is the minimum magnitude of
the force F. parallel to the plane, that will prevent the sled from slipping down the
plane ? (b) What is the minimum magnitude F that will start the sled moving up
the plane ? (c) What value of F is required to move the sled up the plane at
constant velocity ?
3. Calculate the ratio of the drag force on a passenger jet flying with a speed of 1000
km/h at an altitude of 10 km to the drag force on a prop driven transport flying at
half the speed and half the altitude of the jet. At 10 km the density of air is 0.38
km/m^3, and at 5.0 km it is 0.67 kg/m^3. Assume that the airplanes have the same
effective cross-sectional area and the same drag coefficient C.
4. An Airplane is flying in a horizontal flying in a horizontal circle at a speed of 480
km/h. If its wings are tilted 40 degrees to the horizontal, what is the radius of the
circle in which the plane is flying ? Assume required force is provided entirely by
and “aerodynamic lift” that is perpendicular to the wing surface.
5. A 4.0 kg block is put on top of a 5.0 kg. To cause the top block to slip on the
bottom block while the bottom block is held fixed, a horizontal force of at least 12
Newton’s must be applied to the top block. The assembly of blocks is now placed
on a horizontal, frictionless table. Find the magnitudes of (a) the maximum
horizontal force F that can be applied to the lower block so that the blocks will
movie together and (b) the resulting acceleration of the blocks.
6. Figure below shows, a conical pendulum, in which the bob ( the small object at
the lower end of the cord ) moves in a horizontal circle at constant speed. The bob
has a mass of 0.040 kg the string has a length L=0.90 m and a mass that is
negligible relative to the bobs mass,. And the bob follows a circular path of
circumference 0.94 m . What are (a) the tension in the string and (b) the period of
the motion ?
7. The 3 blocks below are released from rest and then accelerate with a magnitude of
0.500 m/s^2. What is the coefficient of kinetic friction between the sliding block
and the table ?