A solid rock, suspended in air by a spring scale, has a measured mass of 8.50 kg

Question

A solid rock, suspended in air by a spring scale, has a measured mass of 8.50 kg. When the rock is submerged in water, the scale reads 4.00 kg. What is the density of the rock? (Density of water 1000 kgm*) 9. a) 3.2 x 102 kg/m" b. 6.8x 102 kg/m3 c. 8.9× 102kg/m" d. 1.9 x 103 kg/m3 e. 1.9% 106 kg/m 3 10. Water pressurized to 3 x 105 Pa is flowing at 6.0 m/s in a pipe which contracts to ? of its former area. W are the pressure and speed of the water after the contraction? (Density of water 1000 kg/m2 a. 3.6 x 105 Pa, 18 m/s b, 3.0 ×105 Pa, 2 m/s c. 3.0 x 105 Pa, 18 m/s d. 1.6 x 105 Pa, 2 m/s e. 1.6 x 105 Pa, 18 m/s If 5 x 104 J are transferred to the rod by heat, what is its change in poC) II. A 2- kg copper rod is 47 cm long at 25°C. length? (For copper: specific heat is c-387 J/kg°C and coefficient of linear expansion is a= 1.7 x 10"s a. 0.052 cm b. 0.078 cm c. 0.232 cm d. 39.950 cm e. More information is needed. Page

Explanation / Answer

9. m = 8.50 kg

Buoyancy force , Fb = (V_submerged)(rho_fluid) g

when submerged in water,

N = W - Fb

4g = 8.50 g - (1000 V) g

V = 4.5 x 10^-3 m^3

rho = m /V = (8.50 kg) / (4.5 x 10^-3) = 1.9 x 10^3 kg/m^3

Ans(d)

10. Q = A1 v1 = A2 v2

(A) (6 m/s) = (A/3) (v2)

v2 = 18 m/s

Using Bernoulli's equation,

P1 + rho v1^2 /2 = P2 + rho v2^2 /2

(3 x 10^5) + (1000 x 6^2 / 2) = P2 + (1000 x 18^2 / 2)

P2 = 1.6 x 10^5 Pa  

Ans(e)

11. Q = m C deltaT  

5 x 10^4 = 2 x 387 x deltaT  

deltaT = 64.6 deg C  

L = L0 (1 + alpha deltaT )

deltaL = L0 alpha deltaT = (47)(1.7 x 10^-5)(64.6)

= 0.052 cm

Ans(a)

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.