Amassless spring with force constant
245 n/m is fastened at its left end to a vertical
wall, as shown below.
the acceleration of gravity is 9.8 m/s
2
.
9 kg 3 kg
245 n/m
initially, the 9 kg block and 3 kg block rest
on a horizontal surface with the 9 kg block in
contact with the spring (but not compressing
it) and with the 3 kg block in contact with the
9 kg block. the 9 kg block is then moved to
the left, compressing the spring a distance of
0.7 m, and held in place while the 3 kg block
remains at rest as shown below.
9 kg 3 kg
k 0.7 m
determine the elastic energy u stored in
the compressed spring.
answer in units of j.
013 (part 2 of 4) 10.0 points
the 9 kg block is then released and accelerates
to the right, toward the 3 kg block. the
surface is rough and the coefficient of friction
between each block and the surface is 0.5 . the
two blocks collide, stick together, and move
to the right. remember that the spring is not
attached to the 9 kg block.
find the speed of the 9 kg block just before
it collides with the 3 kg block.
answer in units of m/s.
014 (part 3 of 4) 10.0 points
find the final speed of both blocks (stuck
together) just after they collide.
answer in units of m/s.
015 (part 4 of 4) 10.0 points
find the horizontal distance the blocks move
before coming to rest.
answer in units of m

Awheel rotates without friction about a stationary horizontal axis at the center of the wheel. a constant tangential force equal to 82.0 n is applied to the rim of the wheel. the wheel has radius 0.150 m . starting from rest, the wheel has an angular speed of 12.8 rev/s after 3.88 s. what is the moment of inertia of the wheel?

Dinate system, and a charge q = - 2.00 nc is placed s2 10 n> c. (a) what is the change in electric potential energy when the dipole moment of a molecule changes its orientation with respect to es from parallel to perpendicular? (b) at what absolute temperature t is the average translational kinetic energy 32 kt of a molecule equal to the change in potential energy calculated in part(: abovethistemperature, thermalagitationprevents the dipoles from aligning with the electric field.) placed in a uniform electric field e with magnitude 1.6 * 6 on the positive x-axis at x = 4.00 cm. (a) if a third charge q3 = +6.00 nc is now placed at the point x = 4.00 cm, y = 3.00 cm, find the x- and y-components of the total force exerted on this charge by the other two. (b) find the magnitude and direction of figure p21.62 ll uu 21.55 . torque on a dipole. an electric dipole with dipole moment ps is in a uniform external electric field es. (a) find the orientations of the dipole for which the torque on the dipole is zero. (b) which of the orientations in part (a) is stable, and which is unstable? (hint: consider a small rotation away from the equi- librium position and see what happens.) (c) show that for the stable orientation in part (b), the dipole’s own electric field tends to oppose the external field. 21.62 ..

An charge with mass m and charge q is emitted from the origin, (x, y)=(0,0). a large, flat screen is located at x=l. there is a target on the screen at y position y(h), where y(h) > 0. in this problem, you will examine two different ways that the charge might hit the target. ignore gravity in this problem. 1.assume that the charge is emitted with velocity v(0) in the positive x direction. between the origin and the screen, the charge travels through a constant electric field pointing in the positive y direction. what should the magnitude e of the electric field be if the charge is to hit the target on the screen? express your answer in terms of m, q, y(h), v(0), and l. 2.now assume that the charge is emitted with velocity v(0) in the positive y direction. between the origin and the screen, the charge travels through a constant electric field pointing in the positive x direction. what should the magnitude e of the electric field be if the charge is to hit the target on the screen? express your answer in terms of m, q, y(h), v(0), and l.