Assignment #2, Physics 204/2-02 and -51 2006 Show your work for all questions.
1. A football in flight is at the point (10 m) i + (50 m) j. The acceleration of the ball is given by a = (-9.81) m/s2) j.
If the velocity of the ball is
v = (2.0 m/s) i + (0.5 m/s) j, what will be its velocity in 0.5 s?
a. v = (-5.0 m/s) j
b. v = (-3.0 m/s) i + (-4.4 m/s) j
c. v = (2.0 m/s) i + (-4.4 m/s) j
d. v = (5.0 m/s) i
e. none of these
2. At the highest point in its path, an arrow is travelling at a speed of
10 m/s. How fast was it moving 0.50 s earlier?
a. 5.0 m/s
b. 11 m/s
c. 15 m/s
d. 1.3 x 102 m/s
e. none of these
3. A book sits on a horizontal top of a car as the car accelerates horizontally from rest. If the static coefficient of friction between the car top and the book is 0.45, what is the maximum acceleration the car can have if the book is not to slip?
(a) 3.21 m/s2 (b) 3.76 m/s2 (c) 4.02 m/s2 (d) 4.41 m/s2
4. during a rescue operation, a man of mass 70.0kg hangs by 2 inextensible cables A and B inclined at 60 degrees to the horizontal.
a) a horizontal pulling force F-> is applied to the man as shown in the figure. the man remains stationary. if F-> has magnitutde 250N , find the magnitutdes of the tensions in the 2 cables.
b) determine the magnitutde of F-> for which the cable B would become slack, ie.e its tension becomes zero.
5. A graduate student (having a mass of 40 kg) is standing inside an elevator on a scale that reads in newtons. Suppose the elevator accelerates upward at one-half the acceleration of gravity (a = 1/2 g) -- what does the scale read?
6. Lunar gravity at the Moon's surface is only 1/6 as strong as what we experience here on the surface of the Earth. Since the diameter of the Moon is about 1/4 as large as the Earth diameter, the lunar mass is about
a. 3 x 10-3 times the Earth mass.
b. 1 x 10-2 times the Earth mass
c. 3/8 of the Earth mass.
d. 1/3 of the Earth mass.
e. 3 times the Earth mass.
7. At what point between the Earth, mass Me, and the Moon, mass 0.0123 Me will their gravitational fields cancel each other (i.e., at what point will a small mass experience zero net force)?
a. At the center of the Earth.
b. At the center of mass of this system.
c. At a distance 50% of the way out from the Earth to the Moon.
d. At a distance 74% of the way out from the Earth to the Moon.
e. none of these.
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) в машине она выпорхнула и уселась на спинку сиденья...и сидела до тех пор,пока он её не взял снова в руки и не вынес на улицу..А потом она улетела.
