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Machines & inclined planes Questions

1.  An inclined plane of length 5m is used to raise a body of mass 60kg to the back of a lorry. If the

 plane is inclined at an angle 25° from the horizontal, calculate the efficiency of the system given

 that a constant force of 650 N is used to push the body up the plane  

 

 

 

Image From EcoleBooks.com2.  Vicky performed an experiment using a pulley system as shown in the figure.

Image From EcoleBooks.com

 

Image From EcoleBooks.com

 

 

 

 

 

ecolebooks.com

Image From EcoleBooks.comImage From EcoleBooks.com

 

 

 

 

 (a) What is the V.R. of the system?

Image From EcoleBooks.com(b) Determine the M.A. of the system.  *

(c) Calculate the efficiency of the system.

(d) Explain why efficiency of a practical machine is always less than 100%

(e) If the load moves a distance of 5 cm. Find the work done on the load.

3.  The figure below shows a pulley system being used to raise a load. Use the information given

Image From EcoleBooks.com   in the figure to answer questions (a) and (b)

 

 

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

 

 (ii) If a load of 100N is raised by applying an effort of 48N, determine the efficiency of

the system.

 

4.  (a) (i) Define the term velocity ratio (V.R)  

(ii) Name one machine that has a velocity ratio of less than one  (V.R < 1)

  (b) The figure below shows a set-up used to find the mechanical advantage of a pulley system

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

 

 

 On the axes provided sketch a graph of mechanical advantage (M.A) against load (L)  

 

 

 

 

 

 

 

 

 

 

 

 

  (c) A hydraulic machine is used to raise a load of 100kg at a constant velocity through a height

  of 2.5m. The radius of the effort piston is 1.4cm while that of the load piston is 7.0cm. Given

that the machine is 80% efficient, calculate:-

  (i) The effort needed

  (ii) The energy wasted in using the machine

 

5.   (i) complete the diagram below to show how the pulley can be used to raise a load L by

applying an effort E  

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

 

 

 

 

(ii) The pulley system above has a mechanical advantage of 3. Calculate the total work done

when a load of 60N is raised through a height of 9M

Machines & inclined planes Answers

1.  M.A = 600M = 0.92307

650M

 V.R = 1 = 2.366

Sin 25  


= M.A = X 100

V.R

  = 0.92307 X100

2.366 = 39.01%

2.  (a) V.R = 5

 

Image From EcoleBooks.com  (b) MA = L

E

Image From EcoleBooks.com   = 4000

  1000

Image From EcoleBooks.com  = 4

Image From EcoleBooks.com

 (c) eff. = M.A x 100%

Image From EcoleBooks.com   VR

Image From EcoleBooks.com = 4/5

= 80%

 (d) Some work is done overcoming friction or lifting the moving parts

Image From EcoleBooks.com

Image From EcoleBooks.com  (e) W = F x d

= 40,000 x 0.05Image From EcoleBooks.com = 2000J

 

3.   VR = 4

A = L = 100

  E 48

u = M.A x 100%

Image From EcoleBooks.comV.R

Image From EcoleBooks.com= 100 x ¼ = 52.08%

  48

 

4.   (a) (i) Velocity ration is the distance moved by the effort to the distance moved by the load

in the same time

(ii) – Pulley belts

– Gears (any one)

(b) Graph

(c) (i) V.R = R2 = 7x 7 = 25

r2 1.4 x 1.4

Efficiency = M.A x 100%

  V.R

M.A = r x V.R = 80 x 25 = 20

  100

E = KL = 100 x 10 = 50N

M.A 20

(ii) EH = work output x 100%

Work input

Work output =mgh

= 100 x 10 x 2.5

= 2500J

80 = 2500 x 100

Work output

Work out put = 2500 x 100 = 3125J

80

Energy lost = 3125 – 2500

  = 625J

5.  i)

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

 

ii) E   = L/M.A

 = 60/3

 = 20N

Total work done by effort

= E x Distance moved by effort

= 20 x 9 x V.R

= 20 x 9 x 4

= 720J




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EcoleBooks | Machines & inclined planes Questions And Answers (part 1)

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