oo H20 11:37 PM session.masteringphysics.com Exercise 3.3 MasteringPhysics A web
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oo H20 11:37 PM session.masteringphysics.com Exercise 3.3 MasteringPhysics A web page designer creates an animation in which a dot on a computer screen has a position of r 3.6 cm +(2.I s2 )t li 4.9 cm/s )tj Part A 0 and 2.0 s. Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. 8.4, 9.8 cm/s vate Give Up Submit incorrect; Try Again; 18 attempts remaining Part B Find the instantaneous velocity at t »0. Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y componentExplanation / Answer
A)
r = [3.6 + (2.1)t2] i +[(4.9)t] j
at t= 0,
r = 3.6 i
At t= 2 s
r = 12 i + 9.8 j
Average velocity
v = dr /dt = [(12-3.6)/(2-0)]i + [(9.8-0)/2] j
v = 4.2 i + 4.9 j
i.e. (4.2,4.9)
B)
dr/dt = [2(2.1)t ]i + 4.9 j
at t = 0
v = 4.9 j
v = (0,4.9)
C) at t= 1 s
[2(2.1)(1)]i + 4.9 j
4.2 i + 4.9 j
D) at t= 2 s
[2(2.1)(2)]i + 4.9 j
8.4 i + 4.9 j
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