# answerkeys5 - F J and Force on Moe F M have same magnitude...

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Answer Key for problems in Unit V. 1. W = mg = 5 . 3kg × 9 . 8m / s 2 = 51 . 94N. 1lb = 4 . 448N, 10 . 6lbs = 10 . 6 × 4 . 448kg = 47 . 149N. 2. 3. F = ma , m = F a = 2000N 2m / s 2 = 1000kg. 4. F = ma , a = F m = 1500N 700kg = 2 . 14 m / s 2 . road. 5. 6. v f and v i are the ﬁnal and initial velocity, respectively. v f = 60mph, v i = 0mph. (a) a = Δ v Δ t = v f - v i Δ t = 60mph 5 . 7s = 60 × 1609m / 3600s 5 . 7s = 4 . 7m / s 2 . (b) F = ma = 900kg × 4 . 7m / s 2 = 4230N. (c) d = 1 2 at 2 = 1 2 4 . 7m / s 2 (5 . 7s) 2 = 76 . 35m . 7. if we let moving direction positive, force will be negative because the applied force is opposite direction (a) F = ma, a = F m = - 7000N 1800kg = - 3 . 89m / s 2 . (b) a = Δ v Δ t , Δ v = v f - v i = a Δ t,v f = 0 v i = - a Δ t = - ( - 3 . 89m / s 2 )6 . 8s = 26 . 452m / s . 8. F net = F J + F K = 120N + ( - 140N) = - 20N a = F net m = - 20N W/g = - 20N 750N / 9 . 8m / s 2 = - 0 . 261m / s 2 . negative sign indicates the acceleration is to the left. So, John is moving to the left. 1

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9. Force on Joe(
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Unformatted text preview: F J ) and Force on Moe( F M ) have same magnitude and opposite direction. Joe’s mass, m J is W J /g = 500N / 9 . 8m / s 2 = 51kg. Moe’s mass, m M is W M /g = 750N / 9 . 8m / s 2 = 76 . 63kg. mass of skateboards m s is 5kg. (a) F J = ( m J + m s ) a J , a J = F J / ( m J + m s ) = 150N / (51 + 5)kg = 2 . 68m / s 2 . (b) F M = ( m M + m s ) a M , a M = F M / ( m M + m s ) = 150N / (76 . 63 + 5)kg = 1 . 84m / s 2 . (c) Joe’s speed = 2 . 68m / s 2 × 3s = 8 . 04m / s. Moe’s speed = 1 . 84m / s 2 × 3s = 5 . 52m / s. 2...
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answerkeys5 - F J and Force on Moe F M have same magnitude...

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