module form 4 physics

8/13/2019 module form 4 physics

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2.5 UNDERSTANDING THE EFFECTS OF A FORCE [../28 x 100 = % ]

1. Answer the following questions.

(a) What are the effects of a force when acting on an object?A force can.

(i)__________ a stationary object

(ii) __________ a moving object

(iii) change the ________ ________ of an object

(iv) change the ________ ________ of an object

(b) !orce is a ( scalar vector ) quantity .

(c) What is the "# unit for force?$he ".#. unit for force is ____________ .

%. !ill in the blan&s with a''ro'riate answers for balance an unbalance forces.

(a) !orces acting on an object are sai balance when the net force is

___________.

(b) When the forces acting on an object are balance it is either at ___________

or moving with ___________ _____________.

(c) An object will ____________________ if the forces acting on it are not balance.

*. +raw the gra'h an state the relationshi' between acceleration a force Fanmass m.

(i)

(m is constant) (! is constant)

(ii) ,elationshi' -

,elationshi' -

aa

a

!

a

m

1

/ 8

1%


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a is __________________ to ! a is __________________ to m

(iii) /ombine the relationshi'-

! 0 & & is constant (& 0 1)

! 0

(b) $he relationshi' between F man ais &nown as 2ewton3s _____________ law

of ____________.

. "olve the following.

(a) A force ! is require to move an object of mass 1444 &g with an acceleration of* m s5%. /alculate ! when(i) object is on a smooth surface(ii) object is on a surface where the frictional force is %44 2

"olution -

(i)

(ii)

!!

a 0a 0 * m s5%

m 0m 0 1444&g&g

a

!


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(b) A bloc& of mass %4 &g is 'ulle along the groun by a force ! of 64 2. $hefrictional force is 14 2. /alculate the acceleration of the bloc&.

"olution-

(c) A car of mass 1%44 &g which is travelling at 74 &m h51comes to a sto' in aistance of 84 m when the bra&es are a''lie. What is the average bra&ing forceof the car?

F


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2.6 ANALYSING I!ULSE AND I!ULSI"E FORCE [ .. / 21 x 100 = .% ]

1. +efine im'ulse an im'ulsive force by com'leting the following table.

"ituation 9:'lanation

A ball of mass mis &ic&ewith a force F.$he time ofcontact is t. $he ballaccelerates from uto v.

!rom - ! 0 ma

! 0 m

! 0t

mv ; mu 0 change of

#m'ulsive force

!t

1

! mumv

! 0t

t

mumv

0 #m'ulsive force is efine as the .........................

. in a collision ore:'losion.

#m'ulse0 force : time

#m'ulse 0 !t 00 change of ..

"# unit for im'ulse is or ..

%) (i) !ill in the blan&s with a''ro'riate answers.

#m'ulsive force is a force which acts over a very .. time interval

uring .. an .

(ii)


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*. $wo eggs of the same mass are release from the same height as shown in

the figure below. 9ggA falls on a concrete floor while egg Bfalls on a thic&fole towel.

=sing !igure A an !igure


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. A tennis ball of mass 8 g travels at a velocity of >4 m s;1immeiately after it isstruc& by a rac&et. $he time of contact between the tennis ball an therac&et is 4.8 ms. /alculate (a) im'ulse an (b) im'ulsive force e:erte on the

ball. "olution -

1


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2.# $EING AARE OF THE NEED FOR SAFETY FEATURES IN "EHICLES[ ./15 x 100 =.. %]

A &'()*+' ,& -* '

D*&3,* '4* ,3'-+* 7 &-7*' 7*-'(3*& ,+ 9*4,*&

S-7*' 7*-'(3*& I3'-+*

ae ashboar To cushion an impact and increases the ______ __________ ofcollision so the __________ _______ produced is thereby reduced

@ea rest

$o 'revent the winscreen from shattering.

________________________(ABS)

Shatter proof___________

Side impact bars

Automatic air____

Head______

Reinforced passener compartment

/rum'le!ones

Safety seat________

"added___________


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Automatic air bag

"afety seat belt

$o minimie the force acting from a sie5 on collision.

Anti5loc& bra&ing system

$o increase the time interval of im'act so that the resultantim'ulsive force is reuce.

2.8 UNDERSTANDING GRA"ITY [ ./ 2# x 100 = . % ]

1. /om'lete the following by fill in the a''ro'riate answer.

a. An object will .. to the surface of the earth because it is 'ulle by

..

b. $he 'ull or force of gravity also &nown as ...

c. When an object falls without encountering any resistance an uner the force of

. only the object is sai to be .

. All objects freely with the same

acceleration regarless of their an

e. $he constant .. of objects falling freely ue

to the force of .. is &nownas

g.

f. ractically a free . can only ta&e 'lace in

. where there is no air resistance.

g. $he region aroun the earth is the #######. fielof the earth.

h. $he gravitational fiel strength is efine asthe ######. ####

acting on a 1 &g mass.

i. When an object falling freely acceleration ue to gravity g $

vacuum

stone

feather

1B


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An object at the surface of the earth e:'eriences gravitational force g 0 .

%. "tate the ifferences between weight an mass in the table below.

Weight Cass

1. the gravitational force act on the object.

%.

*. vector quantity

.

8. "# unit - 2ewton (2)

1.

%. constant quantity everywhere

*.

. base quantity mass 0 m

8.

"olve the 'roblem below

*. A coconut falls from rest an hit the groun after 1.% s.(a) What is the velocity of the coconut just before hits thegroun?(b) /alculate the height of the coconut before it fall.

. A stone is thrown vertically u'wars with a velocity of %4 m s51. #f g 0 14 ms5%calculate(a) the ma:imum height reache

(b) the time ta&en for the stone to return to its original 'osition.

8

%

%


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2.: ANALYSING FORCES IN E;UILI$RIU [ /


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iii) An air'lane flying at a constant velocity. iv) A trolley being 'ushe at a constantvelocity

v)

"olution -

A bo: of mass &g is being 'ulle by a forceof 64 2 at an angle of *4 4to the surface of afloor. /alculate(a) the com'onentof the force which causesthe bo: to move forwar.(b) the acceleration of the bo: if the frictionalforce between the floor an the bo: is 8 2

vi) A man 'ushes a bo: of mass 4 &g is u' anincline 'lane. $he incline 'lane ma&es an angleof *4 4 with the horiontal floor. $he frictional forceacting between the incline 'lane an the bo: is1%4 2. #f the man 'ushes the bo: with a force of44 2 calculate the acceleration of the bo:.

30 0

60 N

4 kg


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vii)

"olution -

A &g trolley is connecte by a ro'e to a loa ofmass 6 &g. $he friction between the table an thetrolley is 18 2. $he loa is then release.

Assuming that the 'ulley is smooth an the ro'e isof negligible mass fin

(a) the resultant force that act on the system(b) the acceleration of the system(c) the tension of the ro'e

viii) $wo loas of mass * &g an 8 &g are connecte by aro'e which 'asses through a smooth 'ulley. #f thesystem is release from rest calculate the accelerationof the 8 &g loa.

"olution -

6 &g

&g"mooth 'ulley

* &g

8 &g


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* !orces in equilibrium

i A bloc& of mass 6 &g is sus'ene vertically by astring tie at E to the string AE

module form 4 physics

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