Download 6.4-6.5 - OoCities

6-4 Connected Object
The several objects tied together motion
Separate these objects draw free body diagram:
(1)Isolate the object
(2)Draw the all external forces
(3)Set up coordinate system
(4)Resolve the force on x, y axes
(5) apply Newton’s second law
m1=3.1kg, m2=4.4kg, find the acceleration?
T
T
m1
m2
Two blocks are connected by a string, as shown
in Figure. The smooth inclined surface makes
an angle of 350 with the horizontal, and the
block on the incline has a mass of 5.7kg. The
mass of the hanging block is m=3.2kg, Find
acceleration.
5.7kg
350
m
M=2kg, µk=0.3, M=4kg, find accelerate and
tension in rope.
M
m
6-5 Circular Motion

v
changing
 
v  v1

a av  2
t


v1  v 2  v
 v2
a
rˆ
r
v1
v2
θ
θ
v3
Object using the acceleration toward center
of circle with magnitude
v2
ac 
r
centripetal acceleration
This force causes circular motion and this
centripetal acceleration is called the
centripetal force.
Ex.
Tension produces centripetal force

T
Friction is centripetal force
Problem:
A ball is bonded at v=3 m/s what is the tension in rope? r=1.2m
(or r=3m) m=2kg
 
T,a
Rounding a corner
A 1200 kg car rounds a corner of radius r-45 m. if the
coefficient of static friction between the tires and the
road is µs=0.82, what is the great speed the car can have
in the corner without skidding.
Banked road:
If a roadway is banked at the proper angle, a
car can round a corner without any assistance
from friction between the tires and the road.
Find the appropriate banking angle for a 900kg car travelling at 20.5 m/s in a turn of radius
85.0m.
N
θ
W