WELCOME to PHYSICS’s WORLD_presentation_Newton's Second Law

8/10/2019 WELCOME to PHYSICSs WORLD_presentation_Newton's Second Law

1/29


2/29

The Meaning of

Force

Determining The

Net Force

Balance and

Unbalance Force

Type of Forces


3/29

Force is pull/push upon anobject resulting from the

objects interaction with

another object


4/29

Contact

Forces

Action-at-a-

Distance Forces

- Frictional

Force

- Normal Force

- Tension Force- Air Resistance

- Applied Force

- Spring Force

- Gravitational

Force- Magnetic Force

- Electrical Force


5/29

Normal Force

Surface

Normal Force


6/29

Pulling Force

motion

Frictonal Force

Surface

Static frictional force () = . N

Kinetic frictional force () = . N


7/29

T1 T2

T3

T4

A

B

Surface


8/29

Air resistanceforce

Weight force


9/29


10/29


11/29


12/29


13/29

N S

NSNS

NS


14/29


15/29


16/29

The table

pushes upwardson the book

Gravity pullsdownwards onthe book

The friction between thetable/book surfacesexcerts a leftwards forceupon the right ward-moving book


17/29

10 N

10 N

40 N40 N

70 N


18/29

Vertical (X axis)

Horizontal (Y axis)

+ =10 N -10 N 0

+40 N -40 N

= 0So, the net force is 70 N on the north-east

direction,


19/29

The accelerat ion o f an ob ject as

produced by a net force is direct ly

propo r t ional to the magn i tude ofthe net force, in the same d irect ion

as the net fo rce, and inversely

propo r t ional to the mass of theobject.


20/29

= a

= m a

F = Newton (N)

m = Kilogram (Kg)a = Acceleration

(m/)


21/29

m

Fa

M

F

a


22/29

= m .

= m .

= m .


23/29

Acceleration have

same direction with

the net Force

Acceleration is

produced by the net

Force

The unbalanced

Forces cause objects

to accelerate

Draw the free-body

Diagram


24/29

You push an object initially at rest, across africtionless floor with a constant force for a

time interval t, resulting in a final speed of v

for the object. You repeat the experiment but

with a force that is twice as large. What timeinterval is now required to reach the same

final speed v ?

a. 4 t

b. 2 tc. t

d. t

e.

1

4t


25/29

Solution :

Acording to Newtons second law : = m a

a =

and

= m .

=

.

2=

.

1

2=

2=

1

2t (D)


26/29

If you push a heavy box that is at rest, you

must exert some force to start it motion.

However, once the box is sliding, you can applya smaller force to maintain that motion. Why?

Answer :

To get the box to slide, you must pushharder than the maximum static frictional

force. Once the box is moving, you need to

push with a force equal to the kinetic

frictional force to maintain the boxsmotion.


27/29

When two objects of unequal mass are hung

vertically over a frictionless pulley of

negligible mass, as figure below. Determine

the magnitude of the acceleration of the two

objects and the tension in the lightweight

cord!


28/29


29/29

= (

+ ) gThus, we get :

Date post:	02-Jun-2018
Category:	Documents
Upload:	puspa-monalisa
View:	219 times
Download:	0 times

WELCOME to PHYSICS’s WORLD_presentation_Newton's Second Law

Documents