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Chrome File Edit View History Bookmarks People Window Help T -1H. 00% Tue 3:17 PM a E c Finder File Edit x Work, Energy a x A Healing Touch x erext my BLINN B Steven x G how to find mu X SG 7-8 Work ar X Secure C Secure https: ecampusd2l.blinn.edu 129/viewContent/1749665Niew & Steven Carpenter A My Home College Physics I-PHYS mu 8.0 kg vo 2.5 m/s H7. A box of marker-gnomes mi is pulled by a box of markers m2. The initial velocity of mi is vo, to the right. Find the speed of the system when m2 hits the ground. m2 5.0 kg no friction H8. (challenge) A box of animal crackers, m 9.0 kg, slides on a horizontal table pulled by a box of lollipops, m2 6.0 kg, hanging over a 1.2 m/s pulley. Initially m is moving to the right with a speed of 1.2 m/s, but the mi system comes to rest after moving 1.8 m. Use the work-energy theorem to find the coefficient of kinetic friction between mi and the table.

Explanation / Answer

H7

Given

Initial velocity Vo = 2.5 m/s

mass m1 = 8.0 kg

mass m2 = 5.0 kg

distance travelled h = 1.4 m

Solution

The acceleration of mass m1 in the absence of friction is

a = m2­g/(m1 + m2)

a = 5 x 9.8 /( 8 + 5)

a = 3.77 m/s2

Final velocity v

v2 = vo2 + 2ah

v2 = 2.52 + 2x 3.77x1.4

v = 4.1 m/s

H8

Given

mass m1 = 9.0 kg

mass m2 = 6.0 kg

Initial speed u = 1.2 m/s

Final speed v = 0 m/s

Distance travelled d = 1.8 m

Solution

Initial KE of the system

E1 = ½ m1u2

E1 =0.5 x 9 x 1.22

E1 = 6.48 J

Final KE of the system

E2 = ½ m1v2

E2 = 0 J

Change in energy E = 6.48 J

Work done by the friction F = 6.48 J

W = Fd

6.48 = F x 1.8

F = 3.6 N

The coefficient of friction = F/mg

µ = 3.6/9 x 9.8

µ = 0.0408 ( no unit)

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