A block slides on a rough horizontal surface from point A to point B. A force (magnitude P = 2.0 N) acts on the block between A and B, as shown. Points A and B are 1.5 m apart. If the kinetic energies of the block at A and B are 5.0 J and 4.0 J, respectively, how much work is done on the block by the force of friction as the block moves from A to B?
a.
?3.3 J
b.
+1.3 J
c.
+3.3 J
d.
?1.3 J
e.
+4.6 J
a
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Density: A hollow sphere of negligible mass and radius R is completely filled with a liquid so that its density is ?. You now enlarge the sphere so its radius is 2R and completely fill it with the same liquid. What is the density of the enlarged sphere?
A. 8 ? B. 4 ? C. ?/2 D. ? E. ?/8
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A longitudinal wave is represented by the equation z(z, t) = -2.0 cm sin(1,200 rad/s t - 20 
z). Another longitudinal wave is represented by the equation z(z, t) = +2.0 cm sin(1,200 rad/s t + 20
z). What is the equation that represents the superposition of the two waves?
A. z(z, t) = +4.0 cm cos(1,200 rad/s t) cos(20
z)
B. z(z, t) = +4.0 cm cos(1,200 rad/s t) sin(20z)
C. z(z, t) = +4.0 cm cos(1,200 rad/s t) cos(20z)
D. z(z, t) = -2.0 cm cos(1,200 rad/s t) sin(20z)
What is the speed of a proton that has been accelerated from rest through a potential difference of 4.0 kV?
a. 1.1 × 10^6 m/s b. 9.8 × 10^5 m/s c. 8.8 × 10^5 m/s d. 1.2 × 10^6 m/s e. 6.2 × 10^5 m/s