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استاذ ممكن مساعدة
particle moves along x-axis according to equation x(t)= 5t^2+6t+4m.the initial speed of the particle is? a-5m/s b-6m/s c-0 d- 15m/s e- 30m/s

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ball is thrown vertically upwards.the magnitude of the acceleration of the ball at the half of its highest point is: a)g b)-g c)0 d)2g e)1/2g