1. A person pulls a block 2 m along a horizontal surface by a constant force F = 20 N. Determine the work done by force F acting on the block.
알려진 바에 따르면:
힘(F) = 20 N
배수량 (s) = 2 m
각도(θ)) = 0
구함 : Work (W)
솔루션 :
W = F d cos θ = (20)(2)(cos 0) = (20)(2)(1) = 40 Joule
2. A force F = 10 N acting on a box 1 m along a horizontal surface. The force acts at a 30o angle as shown in figure below. Determine the work done by force F!
알려진 :
힘(F) = 10 N
The horizontal force (Fx) = F cos 30o = (10)(0.5√3) = 5√3 N
Displacement (d) = 1 meter
구함 : Work (W) ?
해법 :
W = Fx d = (5√3)(1) = 5√3 줄
3. A body falls freely from rest, from a height of 2 m. If 중력에 의한 가속도 10m/s입니다.2, determine the work done by the 중력!
알려진 바에 따르면:
사물 질량 (m) = 1kg
높이(h) = 2m
중력 가속도(g) = 10 m/s²2
구함: Work done by the force of gravity (W)
솔루션 :
W = F d = w h = m g h
W = (1)(10)(2) = 20 줄
W = work, F = force, d = distance, w = 무게, h = height, m = mass, g = acceleration due to gravity.
4. An 1-kg object attached to a spring so it is elongated 2 cm. If acceleration due to gravity is 10 m/s2, determine (a) the spring constant (b) work done by spring force on object
알려진 바에 따르면:
질량(m) = 1 kg
중력 가속도(g) = 10 m/s²2
신장률(x) = 2cm = 0.02m
무게(w) = mg = (1 kg)(10 m/s)2) = 10 kg m/s2 = 10N
구함: Spring constant and work done by spring force
솔루션 :
(a) Spring constant
공식 Hooke의 법칙 :
F = k x.
k = F / x = w / x = mg / x
k = (1)(10) / 0.02 = 10 / 0.02
k = 500 N/m
(b) work done by spring force
W = – ½ kx2
W = – ½ (500)(0.02)2
W = – (250)(0.0004)
W = -0.1 줄
The minus sign indicates that the direction of spring force is opposite with the direction of object displacement.
5. A force F = 10 N accelerates a box over a displacement 2 m. The floor is rough and exerts a 마찰력 Fk = 2 N. Determine the net work done on the box.
알려진 바에 따르면:
힘(F) = 10 N
Force of kinetic friction (Fk) = 2N
Displacement (d) = 2 m
구함: Net work (W그물)
솔루션 :
Work done by force F :
W1 = F d cos 0 = (10)(2)(1) = 20 Joule
Work done by force of kinetic friction (Fk) :
W2 = 에프k d = (2)(2)(cos 180) = (2)(2)(-1) = -4 Joule
회로망:
W그물 = 여1 -W2
W그물 = 20 - 4
W그물 = 16 줄
6. What is the work done by force F on the block.
알려진 바에 따르면:
힘(F) = 12 뉴턴
Displacement (d) = 4 meters
구함 : 업무(W)
솔루션 :
W = F d = (12 Newton)(4 meters) = 48 N m = 48 Joule
7. A block is pushed by a force of 200 N. The block’s displacement is 2 meters. What is the work done on the block?
알려진 바에 따르면:
힘(F) = 200 뉴턴
Displacement (d) = 2 meters
구함 : 업무(W)
솔루션 :
일하다 :
W = F s
W = (200 Newton)(2 meters)
W = 400 N m
W = 400 줄
8. The driver of the sedan wants to park his car exactly 0.5 m in front of the truck which is at 10 m from the sedan’s position. What is the work required by the sedan?
알려진 바에 따르면:
Displacement (d) = 10 meters – 0.5 meters = 9.5 meters
힘(F) = 50 뉴턴
구함: 업무(W)
솔루션 :
W = F s
W = (50 Newton)(9.5 meters)
W = 475 N m
W = 475 줄
9.
Work done by Tom and Jerry so the car can move as far as 4 meters. Forces exerted by Tom and Jerry are 50 N and 70 N.
알려진 바에 따르면:
Displacement (s) = 4 meters
Net force (F) = 50 Newton + 70 Newton = 120 Newton
구함 : 업무(W)
솔루션 :
W = F s = (120 Newton)(4 meters) = 480 N m = 480 Joule
10. A driver pulling a car so the car moves as far as 1000 cm. What is the work done on the car?
알려진 바에 따르면:
힘(F) = 250 뉴턴
Displacement (s) = 1000 cm = 1000/100 meters = 10 meters
구함: 업무(W)
솔루션 :
W = F s = (250 Newton)(10 meters) = 2500 N m = 2500 Joule
11. Based on figure below, if work done by net force is 375 Joule, determine object’s displacement.
알려진 바에 따르면:
작업 (W) = 375 Joule
Net force (ΣF) = 40 N + 10 N – 25 N = 25 Newton (오른쪽으로)
구함: 배수량 (d)
솔루션 :
The equation of work :
W = F s
Object’s displacement :
d = W / F = 375 Joule / 25 Newton
d = 15미터s
12. The activities below w히치 하지 마세요 일 is ...
A. Push an object as far as 10 meters
B. Push a car until a move
C. Push a wall
D. Pulled a box
솔루션 :
The equation of work :
W = ΣF s
여 = 일, F = 정력에도 유리합니다., d = 배수량
Based on the above formula, work done by force and there is a displacement.
정답은 C입니다.
13. Andrew pushes an object with force of 20 N so the object moves in circular motion with a radius of 7 meters. Determine the work done by Andrew for two times 원 운동.
A. 0줄
B. 1400줄
C. 1540 줄
D. 1760 줄
솔루션 :
If the person pushes 휠체어 for two times circular motion then the person and wheelchair return to the original position, so the displacement of the person is zero.
Displacement = 0 so work = 0.
정답은 A입니다.
14. Someone push an object on the floor with force of 350 N. The floor exerts a friction force 70 N. Determine the work done by force to move the object as far as 6 meters.
A. 45 J
B. 72 J
C. 1680 J
D. 2580 J
알려진 바에 따르면:
The force of push (F) = 350 Newton
마찰력(Ffric) = 70 뉴턴
Displacement of object (s) = 6 meters
구함 : 업무(W)
솔루션 :
There are two forces that act on the object, the push force (F) and friction force (Ffric). The push force has the same direction as the displacement of the object because the push force does a positive work. In another hand, the friction force has the opposite direction with a displacement of the object so that the friction force does a negative work.
Work done by push force :
W = F d = (350 Newton)(6 meters) = 2100 Newton-meters = 2100 Joule
Work done by friction force :
W = – (Ffric)(s) = – (70 Newton)(6 meters) = – 420 Newton-meters = – 420 Joule
The net work :
W net = 2100 Joule – 420 Joule
W net = 1680 줄
정답은 C입니다.
15. An object is pushed by a horizontal force of 14 Newton on a rough floor with the friction force of 10 Newton. Determine the net work of move the object as far as 8 meters.
A. 0.5줄
B. 3줄
C. 32 줄
D. 192 줄
알려진 바에 따르면:
Push force (F) = 14 Newton
마찰력(Ffric) = 10 뉴턴
Displacement of object (d) = 8 meters
구함 : 업무(W)
솔루션 :
There are two forces that act on an object, push force (F) and friction force (Ffric).
The push force has the same direction as the displacement of the object so that the push force does a positive work. In another hand, the friction force has the opposite direction as the displacement of the object so that the friction force does a negative work.
Work done by push force :
W = F s = (14 Newton)(8 meters) = 112 Newton meters = 112 Joule
Work done by friction force :
W = – (Ffric)(s) = – (10 Newton)(8 meters) = – 80 Newton meters = – 80 Joule
The net work :
W net = 112 Joule – 80 Joule
W net = 32 줄
정답은 C입니다.
16. Determine the net work based on figure below.
A. 360줄
B. 450줄
C. 600 줄
D. 750 줄
솔루션 :
Work = Force (F) x displacement (d)
Work = Area of triangle 1 + area of rectangle + area of triangle 2
Work = 1/2(40-0)(3-0) + (40-0)(9-3) + 1/2(40-0)(12-9)
Work = 1/2(40)(3) + (40)(6) + 1/2(40)(3)
Work = (20)(3) + 240 + (20)(3)
Work = 60 + 240 + 60
Work = 360 Joule
정답은 A입니다.
17. A piece of wood with a length of 60 cm plugged vertically into the ground. Wood hit with a 10-kg hammer from a height of 40 cm above the top of the wood. If the average resistance force of the ground is 2 x 103 N and the acceleration due to gravity is 10 m/s2, then the wood will enter entirely into the ground after…. hits.
4
B. 16
C. 28
D. 30
알려진 바에 따르면:
Mass of hammer (m) = 10 kg
Acceleration due to gravity (g) = 10 m/s2
Weight of hammer (w) = m g = (10)(10) = 100 kg m/s2
Displacement of hammer before hits the wood (d) = 40 cm = 0.4 meters
The resistance of wood (F) = 2 x 103 엔 = 2000엔
Length of wood (s) = 60 cm = 0.6 meters
구함: The wood will enter entirely into the ground after…. hits.
솔루션 :
Work done on the hammer when hammer moves as far as 0.4 meters is :
W = F d = w s = (100 N)(0.4 m) = 40 Nm = 40 Joule
Work done by the resistance force of the ground :
W = F d = (2000 N)(0.6 m) = 1200 Nm = 1200 Joule
The wood will enter entirely into the ground after…. hits.
1200 Joule / 40 Joule = 30
정답은 D입니다.
[wpdm_package id = '1192 ′]
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