Advertisements
Advertisements
प्रश्न
In following figure, shows a block and tackle system of pulleys used to lift a load.
- How many strands of tackle are supporting the load?
- Draw arrows to represent tension T in each strand.
- What is the mechanical advantage of the system?
- When load is pulled up by a distance 1 m, how far does the effort end move?
- How much effort is needed to lift a load of 100 N?
- What will be it's V.R. if the weight of the movable block is doubled?
उत्तर
(a) 4 stands marked 1, 2, 3, and 4 support the load L.
(b) The strands' tension in the T direction is shown.
(c) M.A. = L = 4T and E = T
M.A. = `L/E`
= `(4T)/T = 4`
(d) As load is pulled up by 1 m
dL = 1m = d
distance moved by effort = dE = nd
V.R. = `d_E/d_L`
= `(nd)/d`
= n = 4m
(e) E = ?
L = 100 N, M.A. = 4
M.A. = `L/E`
`4 = 100/E`
∴ 4E = 100
E = `100 / 4`
E = 25 N
(f) Velocity Ratio of the system = No. of Pulleys = 4
APPEARS IN
संबंधित प्रश्न
A boy has to lift a load of mass 50 kg to a height of 1 m. (a) what effort is required if he lifts it directly? Take g = 10 N kg-1 (b) If the boy can exert a maximum effort of 250 N, so he uses an inclined plane to lift the load up. What should be the minimum length of the plank used by him?
A Woman draws water from a well using a fixed pulley. The mass of bucket and water together is 6 kg. The force applied by the woman is 70 N. Calculate the mechanical advantage. (Take g = 10 m s-2)
In following figure, draw a tackle to lift the load by applying the force in the downward direction.
- Mark in the diagram the direction of load L and effort E.
- If the load is raised by 1 m, through what distance will the effort move?
- State how many strands of tackle are supporting the load?
- What is the mechanical advantage of the system?
In following figure, shows a system of four pulleys, The upper two pulleys are fixed and the lower two are movable.
- Draw a string around the pulleys. Also show the place and direction in which the effort if applied.
- What is the velocity ratio of the system?
- How are load and effort of the pulley system related?
- What assumption do you make in arriving at your answer in part (c)?
A block and tackle system has the velocity ratio 3. Draw a labelled diagram of the system indicating the points of application and the directions of load L and effort E. A man can exert a pull of 200 kgf. What is the maximum load he can raise with this pulley system is its efficiency is 60%?
A single fixed pulley and a movable pulley both are separately used to lift a load of 50 kgf to the same height. Compare the efforts applied in an ideal situation.
A woman draws water from a well using a fixed pulley. The mass of the bucket and water together is 60 kg. The force applied by the woman is 70 N. Calculate the mechanical advantage. [Take g = 10 m/s2].
A machine is driven by a 50 kg mass falling at a rate of 10.0 m in 5s. It lifts n load of 250 kgf. Taking the force of gravity on 1 kg mass as 10 N. Calculate the power input to the machine. If the efficiency of the machine is 60%, find the height to which the load is raised in 5s.
The mechanical advantage of a machine is 5 and its efficiency is 80%. It is used to lift a load of 200 kgf to a height of 20 m. Calculate:
(i) The effort required, and
(ii) The work done on the machine (g = 10 ms−2).
A pulley system has a velocity ratio 3. Draw a diagram showing the point of application and direction of load (L), effort (E) and tension (T). It lifts a load of 150 N by an effort of 60 N. Calculate its mechanical advantage. Is the pulley system ideal? Give reason.
