12-03-2009, 06:04 PM
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#17
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تاريخ التسجيل: Jul 2008
التخصص: طب اسنان
نوع الدراسة: إنتظام
المستوى: الثالث
الجنس: أنثى
المشاركات: 2,545
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رد: الفصل الثاني(فيزياء): الحركة في خط مستقيم
a) if aprticle,s position is ginen by x=4-12t+3t^2 (where t is in second and x is in meter) , what is its velocity at t=1s? b) isit moving in the positive or negative direction of x just then? c)what is its speed just then? d) is the speed increasing or decreasing just then? e) is there ever an instant when the velocity is zero?if so .give the if not answer no. f)is there atime after t=3s when the particle is moving in the negative direction of x? if ,so give the time t : if not answer no. sol. Velocity at 1s= v=dv/dt=0-12+6t=-12+6t a) Vat 1s=-12+6.1=-6m/s b) in the negative c)?? d)? e)v=0 t=2s v=-12+6t 0=-12+6t T=2 The following equation give the position x of a particle in four situation a)x=3t-4 v=dx/dt =3 b)x=-5t^3+4t^2+6 v=-15t^2+8t c)x=2/t^2-4/t v=4t^3-4t^2 d)x=5t^2-3 v=10t اسئله من الكتاب حليتهم وياريت تشوف لو صح ولالا
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