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Unformatted text preview: Physics 110 Spring 2006 Forces in 1 and 2Dimensions – Their Solutions 1. Two forces F 1 and F 2 acts on a 5kg mass. If the magnitudes of F 1 and F 2 are 20N and 15N respectively what are the accelerations of each of the masses below? ( ) ( ) ( ) ( ) 1 2 2 2 , 2 1 , , , 1 2 , 2 , , , 1 2 , 2 , 1 2 2 , , , , 1 2 , 2 , , , 1 2 , 2 , 3 . 25 @ 08 . 6 5 . 27 13 tan @ 5 13 5 . 27 13 60 sin 16 sin 5 . 27 60 cos 15 20 cos tan @ tan @ . 31 @ 5 20 15 tan @ 5 15 20 15 ; 20 tan @ tan @ . 2 2 = = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = + = = = = = + = + = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = + = = → = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = + = = = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = + = = = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = + = = → = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = + = − − − − − − θ θ θ θ θ θ θ θ θ θ s m net y net x net x net y net y net x net net net net x net y net y net x net net s m net y net x net x net y net y net x net net net net x net y net y net x net net N N kg N N a N F F N N N F F F F F m F F m F a ma F F F F F b N N kg N N a N F N F F F m F F m F a ma F F F F F a 2. You stand on the seat of a chair and then hop off. 2. You stand on the seat of a chair and then hop off. a. During the time you are in flight down to the floor, the Earth is moving up toward you with an acceleration of what order of magnitude? a. During the time you are in flight down to the floor, the Earth is moving up toward you with an acceleration of what order of magnitude? b. The Earth moves up through a distance of what order of magnitude? b. The Earth moves up through a distance of what order of magnitude? m m a a x x a x a x t t a x kg kg a a m m a a m a m F F s m s m you Earth you Earth you you Earth Earth Earth Earth s m s m Earth you Earth you Earth you you Earth Earth you Earth 24 22 2 2 2 1 22 24 10 8 . 5 8 . 9 10 2 . 1 50 . 2 2 times. equal for move both you high, 50cm say, is chair that a For b. 10 2 . 1 8 . 9 10 . 6 70 Thus, other. each on forces opposite and equal exert Earth the and you Both a. 2 2 2 2 − − − × = × × = × = → = = → = × = × × = = ∴ = → = 3. The distance between two telephone poles is 50m. When a 1kg bird lands on the telephone wire halfway between the poles, the wire sags 0.2m. a. Draw a free body diagram of the bird. a. 25m θ 0.2m F T2 F T1 m b g b. How much tension does the bird produce in the wire? ( ) N kg g m F g m F ma g m F F F F ma F F F m m b s m b T b T y b T y T T x T T x o 5 . 612 458 . sin 8 . 9 1 sin sin 2 sin 2 : cos cos : 458 . 008 . 25 2 . tan . 2 1 1 1 2 1 2 1 = × = = = → = = − = → = = − = → = = ∑ ∑ θ θ θ θ θ θ θ mg θ 1 = 60 θ 2 =60 y x F T1 F T2 4. A bag of cement of weight 325N hangs from three wires as shown below....
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 Spring '10
 Smith
 Physics, Acceleration, Force, Friction, Mass, Sin, Cos, Fnet

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