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BASIC PHYSICS I (PHY201-02) Summer 2016 QUIZ#1 NAME: An object started from rest

ID: 1415195 • Letter: B

Question

BASIC PHYSICS I (PHY201-02) Summer 2016 QUIZ#1 NAME: An object started from rest and traveled in a straight line A, B, C, D, and beyond. Starting point is 'A' and moving with constant acceleration. Three (3) seconds after start, the object crossed the point 'B', and five (5) seconds (after start) the object crossed the point 'C'. Ten (10 seconds after start, the object crossed point D'. The distance between the points and 'C' is 32 m. Now Calculate (a) the acceleration of the object, (b) the velocity of the object when 'B' object when it crossed the point 'C', (c) the velocity of the crossed point 'D', and (b) the distance between 'A' and 'D'.

Explanation / Answer

Va = 0

a = ? (constant)

t1 = 3 sec reached B

t2 = 5 sec reached C

t3 = 10 sec reached D

Vb = Va + a*t

Vb = 0 + a*3

Vb = 3*a

Sb - Sa = Va*t + 0.5*a*t^2

Sb - Sa = 0*t + 0.5*a*3^2 = 4.5*a

Vc = Va + a*t

Vc = 0 + a*5 = 5*a

Vd = Va + a*t

Vd = 0 + 10*a = 10*a

Sc - Sb = Vb*t + 0.5*a*t^2

32 = 3*a*2 + 0.5*a*2^2

32 = 6*a + 2*a

a = 4m/sec^2 (A)

Vc = 5*4 = 20 m/sec (B)

Vd = 10*a = 10*4 = 40 m/sec (C)

Sd - Sa = Va*t + 0.5*a*t^2

Sd - Sa = 0*10 + 0.5*4*10^2

Sd - Sa = 200 m (D)