Question

Need help with 18 and 20

17. A point on the rim of a 0.8 m radius rotating wheel has a centripetal acceleration of 7 m/s. What is the angular velocity of a point 0.10 m from the center of the wheel? A) 6.4 rad's (リ2.24 rad/s C) 2.96 rad/s D) 0.1143 rad/s E) 1.28 rad/s 18. A 12 kg block rests on a 31° inclined frictionless surface and is attached by a non-slipping light string over a pulley of mass 40.3 and moment of inertia 1- 45 MR2 to a 11 kg hanging mass. Ifg- 9.8 m/s2, what is the tension in the connecting string? A) 95.17N B) 104.16 N C) 132N D) 33.8 N E) 39.6N 19. A block of wood has density o.so gm/em'and mass I500 gm. It floats in a container of oil (the oi's density is 0.6 gm/cm2). What volume of oil does the wood displace? A) 1125N B) 3240N C) 1350 N D) 750 N E 2500 N The pressure in a water tower is 30000 Pascals (N/m2) higher than at an open faucet. Use Bernoulli's equation to determine the velocity of A) 30 m/s B) 31.5 m/s C) 18.9 m/s D) 4.5 m/s E) 14 m/s 20· outlow from the open faucet. If the height difference between the top water level in the tower and the faucet is 7 meters, then the velocity of outflow is Version 4 Page 2

Answer 1

Answer (20) From Bernoulli’s Equation, we have:

Head at Tower side = Head at Faucet side

=>(P₁/ρg) + (v₁²/2g) + (z₁) = (P₂/ρg) + (v₂²/2g) + (z₂)

[ Given P₁ – P₂ = 30000 Pa, ρ = 1000 kg/m³(density of water), g=9.81m/s², v₁=0 as level of water in water tower will decrease at infinitesimally slow rate, z₁ - z₂ = 7 m ]

=>(P₁ – P₂)/ρg + (z₁ - z₂) = (v₂²/2g)

=>(P₁ – P₂)/ρ + g(z₁ - z₂) = (v₂²/2)

=>(30000)/1000 + 9.81*7 = (v₂²/2)

=>v₂ = 14 m/s    Answer (Option E)