연세대 일반물리학(대학물리학) 2022-1 기말 기출문제 (정답 포함) 

연세대 일반물리학(대학물리학) 2022-1 기말 기출문제 (정답 포함) 

 

 

1. 시험 정보

 

학교/과목	연세대 일반물리학(대학물리학)
시험명	2022-1 기말고사
문항수/형식	단답형, 서술형
교수명	-
정답/해설	✅ 있음
파일형식	-

 

 

2. 출제 범위 & 키워드

 

 

 

 

3. 기출 미리보기

문제

A fire occurs in a building at the height of 40 m and a fire truck arrives at the
position 20 m away from the fire place. The fire truck has a fire hose with a
diameter of 10 cm and a nozzle having a diameter of 2 cm at the end of the fire
hose. The fire man can go up to the height of 20 m using a ladder and then
sprout the water with an initial pressure of 104 Pa at the nozzle.

(a) Estimate the minimum speed of water from the nozzle to reach the fire source
located at the height of 40 m in the building.

(b) Find the corresponding speed of water flowing in the fire hose.

(c) Calculate the minimum pressure needed to push the water in the fire hose for
extinguishing the fire. Assume that the density of water is 1000 kg/m3 and the
acceleration of gravity is 10 m/s2.

답

(a)수평거리 𝑥=20, 상대높이 y=20 m로 목표점을 맞히는 포물선에서 필요한 최소 발사속도:

[10*{(400+400)^0.5+20}]^0.5==22m/s, 

(b)연속방정식 : A_hose*v_hose=A_nozzle*v_nozzle
지름 비 : D_hose : D_nozzle = 10 : 2 = 5 : 1
A 비 : 25 : 1
∴v_hose = A_nozzle/A_hose * v_nozzle = 1/25 * 22  = 0.88m/s

(c)펌프(지면, z=0) → 노즐 출구(z=20 m)까지 베르누이:
P_pump / rho + v_hose^2 /2 + g*z_pump = v_nozzle^2 / 2 + g*z_nozzle
∴P_pump = 1000[{22^2-0.88^2}/2+10*20]Pa = 440000Pa

 

4. 자료 보기

 

 

[기출 문제]

 

A fire occurs in a building at the height of 40 m and a fire truck arrives at the position 20 m away from the fire place. The fire truck has a fire hose with a diameter of 10 cm and a nozzle having a diameter of 2 cm at the end of the fire hose. The fire man can go up to the height of 20 m using a ladder and then sprout the water with an initial pressure of 104 Pa at the nozzle. (a) Estimate the minimum speed of water from the nozzle to reach the fire source located at the height of 40 m in the building. (b) Find the corresponding speed of water flowing in the fire hose. (c) Calculate the minimum pressure needed to push the water in the fire hose for extinguishing the fire. Assume that the density of water is 1000 kg/m3 and the acceleration of gravity is 10 m/s2.

 

 

[정답]

 

(a)수평거리 𝑥=20, 상대높이 y=20 m로 목표점을 맞히는 포물선에서 필요한 최소 발사속도: [10*{(400+400)^0.5+20}]^0.5==22m/s,  (b)연속방정식 : A_hose*v_hose=A_nozzle*v_nozzle 지름 비 : D_hose : D_nozzle = 10 : 2 = 5 : 1 A 비 : 25 : 1 ∴v_hose = A_nozzle/A_hose * v_nozzle = 1/25 * 22  = 0.88m/s (c)펌프(지면, z=0) → 노즐 출구(z=20 m)까지 베르누이: P_pump / rho + v_hose^2 /2 + g*z_pump = v_nozzle^2 / 2 + g*z_nozzle ∴P_pump = 1000[{22^2-0.88^2}/2+10*20]Pa = 440000Pa