Title कक्षा ९,विज्ञान, बल, नेपाली+अङ्ग्रेजी माध्यम.pdf ✅

1 an Force 1. rfn / lj>fdsf] kl/efiff lbg'xf];\. Define motion and rest. pQ/M j/k/sf j:t'x?sf] ;fk]Ifdf s'g} j:t'n] cfˆgf] :yfg kl/jt{g ub{5 eg] pSt j:t'sf] l:yltnfO{ rfn elgG5 . When an object changes its position with respect to its surrounding objects, it is said to be in motion. j/k/sf j:t'x?sf] ;fk]Ifdf s'g} j:t'n] cfˆgf] :yfg kl/jt{g ub}{g eg] pSt j:t'sf] l:yltnfO{ lj>fd elgG5 . When an object does not change its position with respect to its surrounding objects, it is said to be in rest. 2. ...rfn / lj>fd ;fk]lIft zAbfjfnL x'g\Ú eGg] tYonfO{ pbfx/0f;lxt k'li6 ug'{xf];\. 'Motion and rest are relative terms.' Justify this statement with suitable example. pQ/M ...rfn / lj>fd ;fk]lIft zAbfjfnL x'g\Ú lsgls Pp6f j:t' csf]{ s'g} Ps j:t'sf] ;fk]Ifdf rfndf x'g ;S5 eg] pSt j:t' ;f]xL ;dodf csf]{ s'g} j:t'sf] ;fk]Ifdf lj>fd cj:yfdf x'g ;S5 . h:t}M u'l8/x]sf] a;df ofqf ubf{ a; leqsf ofq' a;sf] ;fk]Ifdf lj>fd cj:yfdf x'G5g\eg] ;f]xL a]nf ;8ssf] ;fk]Ifdf rfn cj:yfdf x'G5g\. 'Rest and motion are relative terms' because an object may be in motion with respect to one object. But at the same moment, the same object may be in rest with respect to another object. For example: while travelling in a bus, the passengers in it are at rest with respect to the bus, but at the same time, they feel themselves in motion with respect to the trees, electric poles, houses, etc. present along the road side. 3. :yfgfGt/0f eGgfn] s] a'lemG5 < What is meant by displacement ? pQ/M lglZrt lbzflt/ j:t'n] kf/ u/]sf] b'/LnfO{ :yfgfGt/0f elgG5 . Ps hgf JolQm 4 ld6/ k"j{lt/ uof] eg] p;sf] :yfgfGt/0f 4 ld6/ k"j{ x'G5 . o;df 4 ld6/ dfg xf] eg] k"j{ lbzf xf] . The distance covered by a body in a fixed direction is called displacement. If a person moves 4 m towards east, his displacement is 4 m due east. Here, 4 m is magnitude and east is direction. 4. j]u / ult larsf] leGgtfM Differences between speed and velocity: qm=;+= S.N. j]u Speed qm=;+= S.N. ult Velocity != s'g} j:t'n] PsfO ;dodf kf/ u/]sf] b'/LnfO{ j]u elgG5 . The distance covered by a body per unit time is called speed. != s'g} j:t'n] PsfO ;dodf kf/ u/]sf] :yfgfGt/0fnfO{ ult elgG5 . The displacement covered by a body per unit time is called velocity. @= of] :s]n/ /fzL xf] . It is a scalar quantity. @= of] e]S6/ /fzL xf] . It is a vector quantity. #= o;sf] dfg z"Go x'Fb}g . It cannot be zero. #= o;sf] dfg z"Go klg x'g ;S5 . It can be zero. $= j]u (speed) = दरुी (distance) समय (time) $= ult(velocity)= स्थानान्तरण(displacement) समय (time) 5. ultnfO{ lsg e]S6/ kl/df0f elgG5 < Why is velocity called vector quantity ? pQ/M ultsf] dfg / lbzf b'j} x'g] ePsfn] of] e]S6/ /fzL xf] . Velocity has both magnitude and direction. So, it is called vector quantity.

3 S.I. unit of acceleration is m/s2 and its formula is given by: k|j]u (acceleration) = गतत पररवततन(Change in velocity) लागेको समय (time taken) i.e. a = v−u t 11. ult ;DalGw ;lds/0fx? (Equations of motion): i) v = u + at ii) S = u+v 2 × 2 iii) S = ut + 1 2 at 2 iv) v 2 = u 2 + 2aS 12. a, v, u / t sf] ;DaGw :yflkt ug'{xf];\. Establish the relationship among a, v, u and t. or, v = u + at ;DaGw k|dfl0ft ug'{xf];\. Prove the relation v = u + at. pQ/M dfgf}, Pp6f a:t'nfO{ A :yfgaf6 rNg ;'? u/L B :yfg;Dd k'Ug 't' ;do nfUof] . 'A' :yfgdf /xFbf a:t'sf] ult -;'?sf] ult_ 'u' / B :yfgdf cfOk'Ubfsf] ult -clGtd ult_ 'v' 5 eg] k|j]usf] kl/efiff cg';f/, Let, a body reaches from place A to place B in time 't'. If the velocity of the body at place A (initial velocity) be 'u' and at place B (final velocity) be 'v', then From the definition of acceleration, k|j]u (acceleration) = गतत पररवततन(Change in velocity) लागेको समय (time taken) i.e. a = v−u t or, v - u = at ∴ v = u + at Proved. 13. s = u+v 2 × 2 ;"q k|dfl0ft ug'{xf];\. Prove the formula, s = u+v 2 × 2. pQ/M dfgf}, Pp6f a:t'nfO{ A :yfgaf6 rNg ;'? u/L B :yfg;Dd k'Ug 't' ;do nfUof] . 'A' :yfgdf /xFbf a:t'sf] ult -;'?sf] ult_ 'u' / B :yfgdf cfOk'Ubfsf] ult -clGtd ult_ 'v' 5 / tL b'O{ :yfglarsf] b'/L 'S' eP, Let, a body reaches from place A to place B in time 't'. If the velocity of the body at place A (initial velocity) be 'u', at place B (final velocity) be 'v' and distance between those places be 'S', then