Phys 135 A
Hw 5
Note: Q is for Question, P for Problem, and they are from Giancoli 6th Edition Chapter 4
and 5
Chapter 4:
1-P31- (II) Figure 4–49 shows a block
( )
1
mass m
on a smooth horizontal surface,
connected by a thin cord that passes over a pulley to a second block
( )
,
2
m
which
hangs vertically. (a) Draw a free-body diagram for each block, showing the force of
gravity on each, the force (tension) exerted by the cord, and any normal force. (b)
Apply Newton’s second law to find formulas for the acceleration of the system and
for the tension in the cord. Ignore friction and the masses of the pulley and cord.
2-48- (II) Two crates, of mass 75 kg and 110 kg, are in contact and at rest on a horizontal
surface (Fig. 4–54). A 620-N force is exerted on the 75-kg crate. If the coefficient of
kinetic friction is 0.15, calculate (a) the acceleration of the system, and (b) the force
that each crate exerts on the other. (c) Repeat with the crates reversed.Q7. Why
might your foot hurt if you kick a heavy desk or a wall?
3-P55- (II) An 18.0-kg box is released on a 37.0º incline and accelerates down the incline
at
.sm 270.0 2
Find the friction force impeding its motion. How large is the coefficient
of kinetic friction?
4- P76- A 28.0-kg block is connected to an empty 1.35-kg bucket by a cord running over
a frictionless pulley (Fig. 4–59). The coefficient of static friction between the table
and the block is 0.450 and the coefficient of kinetic friction between the table and
the block is 0.320. Sand is gradually added to the bucket until the system just begins
to move. (a) Calculate the mass of sand added to the bucket. (b) Calculate the
acceleration of the system.
