34 n 27 0 13 n 51 0 1/ 1 cm:5n 2/ 1 cm:2n. 1 cm:4 n 20 0 6.5 cm 26n 10 n 1 cm:10 n 4.2 cm 42n 42n 46...
TRANSCRIPT
34 N
270
13 N
510
1/ 1 cm:5N 2/ 1 cm:2N
1 cm:4 N
200
6.5 cm 26N
10N
1 cm:10 N
4.2 cm 42N
42N
460
1 cm:8 N1 cm:3 N
Fx = 40 N Fy = 0
Fx = 0
Fy = -6 N
Newton’s 1st Law of Motion:
If the ____________________ force, Fnet, acting
on an object equals ________, then that object has____________________ . Its acceleration a = _____ .It is said to be in __________________ .
zero
constant velocity
net (resultant)
equilibrium0
Because forces are ______________ and have____________ , the x and y _______________ of the forces often must be added up _______________when there are forces along different _________.
Fnet = 0 really means:________ = 0
________ = 0
vectorsdirection components
separately
net Fx
net Fy
axes
Ex: A 20-N box on a tableat rest
20-N
FN = 20N
w = 20 N
Ex: A 20-N box at rest on a table being pushed down with a 5 N force.
"At rest" __________
20-N
Free body diagrams:
w = FN
5-N
w = 20 N
5 N
FN = 25 N
"At rest" _______________w + push = FN
Both of these boxes are in ___________________ .equilibrium
Ex: Same box sliding to the right on a horizontalfrictionless table at a constant velocity 2.0 m/s
20-N
FN = 20N
Draw only the __________ , not the ____________
Notice:1/ The free body diagram is the _________ as thefirst example. Both are in ___________________ .2/ No force is ___________ to keep box moving.The box will continue its motion ________________.
equilibrium
v = 2.0 m/s
forces velocities
needed
forever
w = 20N
same
"constant velocity" __________w = FN
Ex: The forces acting on a 20-N box are shown at right:
FN = 20N
w = 20 N
pull= 10N
Ff = 10 N
This box is in ___________________. It is either:
1/ _____________ (constant velocity = _____);
2/ or _____________ at a constant velocity.
Unless other information is given, it is _______________ to tell if it is at rest or moving.
at rest
moving
equilibrium
0
impossible
3.0 N
4.0 N
Ex. The three forces below are the only onesacting on an 2.0-kg object. What is the acceleration of the object?
5.0 N
This object could be _______________ or moving with ____________________________ .
0
at restconstant velocity
The net force Fnet = _____ so a must = ____ .0
Add them up:
4.0 N
3.0 N
5.0 N
Restatement of 1st Law: If an object is ____________ or moving with _____________________, it is_________________.
Then the net force (Fnet ) acting on it _________ .
lift = 1.3 MN
w= 1.3 MN
thrust = 300 kN
Ff (drag)= 300 kN
weight ≈ 1.3 x 106 Nthrust ≈ 75 x 103 N/engine x 4 engines
at restconstant velocity in equilibrium
= 0
Ex: A B-2 bomber flying at constant velocity:
The“air force”
Ex. The two forces shown below act on an object. What third force is needed to produceequilibrium?
F1
First way to solve:• Find resultant force F• The answer is -F:
F
-F
-F ___________________ the other two forces.
F2
balances
Second way to solve:1. Add the two forces using head to tail method.2. Add a force to "bring the total force to zero."
original
Notice:• Both ways give ________________________• -F is NOT the ________________ of the other vectors. It is the force that ________________
the other vectors, making Fnet =________. It is
sometimes called the ________________ because it is what is needed to produce ___________________ .
the same result
resultant"balances out"
equilibrantequilibrium
-F
F1
F2
F1F2
head to tail:
0
wire
beam
build
ing
weight
Ex. Draw the vector that represents the force that the beam exerts on point A.
A A
T
w
beamforce
The beam force is the ________________ . It must be added to the other forces so that ___________
equilibrantFnet = 0
Ex. Increasing angle between 2 wires supporting a picture:
Case 1: vertical wires
Case 2: greater angle
Case 3: even greater angle
10 N
w = 10 N
T = ____in eachwire
w = 10 N
w = 10 N
10 N
10 N
1 2
1 12 2
12
1 2
T = ____in eachwire
T = ____in eachwire
As increases, the tension _______________ .
51 2
7
10
increases
A net force is ________________ to maintain motion. An object will maintain its motion in the ________________ of a net force. This idea was discovered by _____________. An object in motion tends to ____________________ , and anobject at rest tends to _________________ . The _______________________ that “makes” this true is called its ___________ .
more __________ more___________in
ert
iamass
Ex. What has more inertia, a truck or a baseball?
property of matter
inertia
absence
not needed
Galileostay in motion
stay at rest
massinertia
truck
Inertia is the tendency of an object to _________________________ . More inertia (mass) means it is __________________ for an object to…1/ …_____________________ when it is at rest;2/ … __________ when it is already moving; and,3/ … ____________________ from a straight path.In other words, ______________ is why an objectneeds __________________ to maintain its motion.This is why Newton's _____________ is calledthe ________________ .
resist changes in motion
more difficultstart moving
stopmove sideways
Law of Inertia
1st Law
no net forceinertia
Fnet a
equilibrium
= 0 = 0
Lawof
Inertia
Open your 3-ring binder to theWorksheet Table of Contents.
Record the title of the worksheet:
Newton’s First Law WS