# Definition for every action there is an equal and

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Definition:“For every action there is an equal and opposite reaction. The force acted on each body are equal in magnitude and in opposite direction.”baabFF5.1 Newton’s Laws of Motion cont
ZSMAHMUD/UiTMCawanganPerak/PHY11012Normal force, FNis the force exerted on an object that is perpendicular to the surface of contact.5.2 Gravity & Normal ForceGravitational force, W is the force exerted on an object due to the attraction of gravity, also called as weight.
ZSMAHMUD/UiTMCawanganPerak/PHY11013Weight, 𝑾Is defined as the force exerted on a body under gravitational field.A vector quantityDependent on location (because gvaries with location)Always directed towards the earth’s center or same direction of acceleration due to gravity, g.S.I. unit: kg m?−2or newton (N).𝑊=?𝑔𝑾𝑾5.2 Gravity & Normal Forcecont
ZSMAHMUD/UiTMCawanganPerak/PHY11014surfaceFNW5.2 Gravity & Normal Forcecont
ZSMAHMUD/UiTMCawanganPerak/PHY11015Free body diagram is a diagram to show all forces acting on an object in a given situation without the body.4 Steps taken to draw a free body diagram:Free Body DiagramamFFnetFor along x-axisFor along y-axisyyamFxxamFi.Identify all forces acting on the object.ii.Draw all forces acting on the object. iii.If it involves more than one object, draw a separate free body diagram for each object.iv.Apply the equation below:5.3 Applications of Newton’s Laws
16Object static (not moving).Forces on the object:1.Normal force, FN2.Weight of object, W = mgExample 1: If an object at equilibrium on horizontalsurfacesFNmgFy= 0FNmg = 0 FN= mgfloorZSMAHMUD/UiTMCawanganPerak/PHY110Fx= 05.3 Applications of Newton’s Laws–cont
17Object hanging (not moving).Forces on the object:1.Tension force, T2.Weight of object, W = mgExample 2: If an object at equilibrium on vertical surfaces (hanging object)Fy= 0T W = 0T mg = 0T = mgTW = mgropeceilingZSMAHMUD/UiTMCawanganPerak/PHY110Fx= 05.3 Applications of Newton’s Laws–cont
Exercise 5.3.1a)Draw free body diagram and find tension on the object given where mass of the picture is 10 kg. (Ans.: 98.1 N)Applications of Newton’s Laws–contb)Draw a free body diagram and find tension on the strings. Given mass of
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5.3 Applications of Newton’s Laws–cont
19Object moving: (x-direction)Forces on the object:1.Normal force, FN2.Weight of object, W = mg3.Pulling force, FExample 3: If an object accelerates on horizontal surfaces (frictionless)Fx= ma; F = maFNmgF (pull)afloorZSMAHMUD/UiTMCawanganPerak/PHY110Fy= 0; FNmg = 0FN= mg5.3 Applications of Newton’s Laws–cont
20Example 4: If an object accelerates on horizontal surfaces with force having w.r.t. x-axis(frictionless)Fx= ma; F cos = maFNmgmgaZSMAHMUD/UiTMCawanganPerak/PHY110Fy= 0; FN+ F sin mg = 05.3 Applications of Newton’s Laws–cont
21Example 5: If an object accelerates on inclinedsurfaces (frictionless)mgmgFx= ma; F mg sin = maZSMAHMUD/UiTMCawanganPerak/PHY110Fy= 0; FNmg cos = 05.3 Applications of Newton’s Laws–cont
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