Question

1. A 12m window hanging scaffolding basket supporting an 80Kg man and paint material? The scaffolding is hanging by a steel rope at eacch end. The basket weight is 40 Kg, the paint is 25Kg located at the middle. The man is located at the middle.

1. Draw the forces diagram.

2. What are the forces F1 and F2 at the ropes holding the basket at the ends?

b) The man moves 4 meters towards F2, will F1 & F2 change?    

c) Find the new F1 & F2 forces exerted on the scaffolding in b above. ∑Ƭ cw=∑Ƭccw & Ƭ=Fd?

         

2. Two cars of equal weights of (1400lb each) were subject to an inelastic head-on collision. One car was traveling eastbound at 50mi/h speed and the other car was traveling westbound at 60mi/h speed.   

1. What was the direction of the motion after collision?         

2. What was the speed after collision? m1V1+m2V2=(m1+ m2)V’ ;  

3. How far they went after 1.4 seconds? convert V to ft/s; S=(V)’.(t)

3. Two men exert 115 lb force each to push a car for distance of 150 feet.

1. What is the Work done in lb ft? W=F.S   

2. What is the power exerted after 5 minutes? P=W/t  

3. If the road is at an angle of 15o uphill. What is the mechanical advantage of the road?

4. What is the force of the effort required to move the 1000lb car the 150 ft in c above?

  

4. A submersible gasoline pump was used to lift 210 gallons/min of gasoline from the bottom of a tank 20 ft below ground level. (One gallon gasoline is 6.3 lb)

1. What is the power rating of the submersible pump? P=W/t= F.S/t    

2. How many gallons can be lifted in 10 minutes?   

5. A 1000 lb box was moved using inclined plane (h=5ft and L=20ft: MA=L/h), a wheel and axle simple machine (wheel diameter is 2 ft and the axle is 0.5 ft: MA=D/d) and 3 pulleys with 3 movables strands.

1. Find the Mechanical Advantage of the inclined plane and the wheel and axle

2. Find the MA of the system (MA = MA1 x MA2 x MA3)

3. Find the exerted effort.

6. True or False questions.

	Question	T/F
a	Angular velocity is measured in RPM or radians per seconds
b	Using 3 gears connected directly, we obtain opposite direction of rotation
c	Friction free machine does not exist commercially and it is costly to make
d	One Horsepower UOM and equal to 550 lb ft/s
e	A wheelbarrow is 2 simple machines named the lever and the wheel & axle.
f	Forces are at equilibrium if the sum of their x & y components are Zeros
g	To convert mi/hr to ft/s; we multiply by 5280
h	To Convert Km/hr to m/s; we multiply by (1000/3600)
i	Impulse = the product of the object mass & change in velocity
j	When the Kinetic Energy and Potential energy are equal in a roller coaster, the height of the car will be: h = ½ (Constant/m.g) , Constant=PE+KE

Answer 1

a) With the man standing in the middle the foroces on the ropes are given by:

In this case W is the weight of the basket plus the man and the paint bucket:

b) If the man moves 4 meters then F₁ and F₂ will change

c) In this situation we can write

2) a) Since the masses of the cars are the same and the car going west is going faster, after the collision the system will go west

b) The speed after the collision is:

(the minus indicates the dir is west)

c) Given that 5 mi/hs = 7.3 ft/s

3) a) The work done is:

b) After 5 min the power excerted is:

c) The MA of the road is:

d) The effort required is:

4) The power of the pump is:

After 10 min:

5) The MA of the incline:

The MA of the wheel and axle:

The MA of the pulley system is 3, then the MA of the system is equal to:

The excertedd effort:

6) a) T

b) F

c) T

d) T

e) T

f) T

g) F

h) T

i) T

j) T