Problem 1: Explain your work.
The sled dog drags sleds A and B across the snow. The coefficient of kinetic friction
between the sleds and the snow (k)is given. The tension in rope 1 is also given.
T1 =TAB =150N
mA=100 kg (12)
mB=80 kg
k=0.1
a. Draw free-body diagrams for each of the blocks in the spaces provided. Make sure to
label each force clearly using double subscripts. Include coordinate systems.
FBD of block: A
FBD of block: B
Indicate Newton’s third law force pair(s).
b. Set up Newton’s 2nd law equations. Number the equations.
F
A:
F
F
B:
F
x

y

x

y

What is the acceleration constraint?
c. Find the acceleration a (magnitude and direction). State which of the above equations
you use.
d. Find the tension T2. State which of the above equations you use.
e. Compare the net forces on A and B.
B
a. FnetA  Fnet
B
b. FnetA  Fnet
B
c. FnetA  Fnet
Problem 2: Explain your work.
Block A is located on top of block B. The lower block B is pulled on by a rope with a
tension of P=20 N. The coefficient of kinetic friction between the lower and upper block
is the same as that between block B and the table.
P =20N
mA=1 kg (12) mB=2 kg
k=0.3
a. Draw free-body diagrams for each of the blocks in the spaces provided. Make sure to
label each force clearly using double subscripts. Include coordinate systems.
FBD of block: A
FBD of block: B
Indicate Newton’s third law force pair(s).
b. Set up Newton’s 2nd law equations. Number the equations.
F
A:
F
F
B:
F
x

y

x

y

What is the acceleration constraint?
c. Find the acceleration a (magnitude and direction) of block B. State which of the above
equations you use.
d. Compare the net forces on A and B.
B
a. FnetA  Fnet
B
b. FnetA  Fnet
B
c. FnetA  Fnet