Block and Tackle System
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What Is The Use Of Law Of Machine
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. (a) What is the maximum load he can raise with this pulley system if its efficiency is 60% ? (b) If the effort end moves a distance 60 cm, what distance does the load move ?
Draw a diagram of a block and tackle system of pulleys having a velocity ratio of 5. In your diagram indicate clearly the points of application and the directions of the load L and effort E. Also mark the tension T in each strand.
A coolie carrying a load on his head and moving on a frictionless horizontal platform does no work. This is because
The coolie is not applying force on the load
The load is stationary
Force and displacement are parallel to each other
Force and displacement are perpendicular to each other
In fig shows a block and tackle system of pulleys used to lift a load .
(a) How many strands of tackle are supporting the load ?
(b) Draw arrows to represent tension T in each strand.
(c) What is the mechanical advantage of the system ?
(d) When load is pulled up by a distance 1 m, how far does the effort end move ?
(e) How much effort is needed to lift a load of 100 N ?
Give reasons for the following :
(a) In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
(b) The efficiency of a movable pulley is always less than 100%.
(c) In case of a block and tackle system, the mechanical advantage increases with the increase in the number of pulleys.
(d) The lower block of a block and tackle pulley system must be of negligible weight.
A block and tackle system has 5 pulleys. If an effort of 1000 N is needed in the downward direction to raise a load of 4500 N, calculate :
(a) the mechanical advantage ,
(b) the velocity ratio, and
(c) the efficiency of the system.
An ideal block and tackle system of 5 pulleys consist of 3 pulleys in the upper block and 2 pulleys in the lower block. If the load is raised by 1 m, through what distance will effort move.
1m
3m
5m
7m
- 90
In fig. draw a tackle to lift the load by applying the force in the downward direction.
(a) Mark in the diagram the direction of load L and effort E.
(b) If the load is raised by 1 m, through what distance will the effort move ?
(c) State the number of strands of tackle supporting the load.
(d) What is the mechanical advantage of the system ?
In fig shows a system of four pulleys. The upper two puleys are fixed and the lower two are movable.
(a) Draw a string around the pulleys.Also show the point of application and direction in which the effort E is applied.
(b) What is the velocity ratio of the system ?
(c) How are load and effort of the pulley system related ?
(d) What assumption do you make in arriving at your answer in part (c) ?
A block and tackle system have VR = 5. Rohan exerts a pull of 150 kgf. What is the maximum load he can raise with his pulley system if its efficiency = 75%?
5000 N
5500 N
5625 N
5600 N
- 8
Mark the fulcrum, load, and effort in the picture of the hammer.
The mechanical advantage of a broomstick is __________.
always equal to one.
always less than one.
always greater than one.
dependent on where it is held.
What is the relation between the load and the effort in the pulley system shown below:
L= 5E
E = 4L
L = E
L = 4E
In a block and tackle system consisting of 3 pulleys, a load of 75 kgf is raised with an effort of 25 kgf. Find : (i) the mechanical advantage, (ii) the velocity ratio, and (iii) the efficiency.
For a single fixed pulley, an effort of 400N is required for a load of 300N. If the effort is moved by 30cm then calculate the efficiency of the pulley & energy that is used in overcoming friction.
60%, 15 J
90%, 45 J
45%, 60 J
55%, 90 J
75%, 30 J
A block and tackle system of 5 pulleys is used to raise a load of 50 kgf steadily through a height of 20 m. Calculate the effort and MA
120 N and 4.17
180 N and 4.25
150 N and 4.15
12 N and 4.30
90 N and 4.34
- 122.2 N
- 222.2 N
- 322.2 N
- 422.2 N
A block and tackle system have the velocity ratio 3. A man can exert a pull of 200 kgf. What is the maximum load he can raise with this pulley system if its efficiency is 50%?
300 kgf
360 kgf
600 kgf
180 kgf
A pair of scissors has its blades 15 cm long, while its handles are 7.5 cm long. What is its mechanical advantage?
2
1
0.5
0.75
what is hooke s law?
In a single fixed pulley, the velocity ratio is always less than the mechanical advantage.
True
False
A block and tackle pulley system has five pulleys in all and is 90% efficient. Calculate the effort required to lift a load of 1000N.
222.22N
2000N
200N
400N
(b) Can a simple machine act as a force multiplier and a speed multiplier at the same time?
(c) A block and tackle system of pulleys has a velocity ratio of 4. (i) Draw a labeled diagram of the system indicating clearly the points of application and directions of load and effort. (ii) What is the value of the mechanical advantage of the given pulley system if is an ideal pulley system?
(ICSE Exam. 2013)
A combination of a movable pulley P1 with a fixed pulley P2 is used for lifting up a load W. If the free end of the string moves through a distance x, find the distance by which the load W is raised.
2 x
x/2
x2
x
A heavy car can be lifted quite easily with a screw.
- True
- False
(b) If the velocity ratio of a machine is 3.6 and the load of the machine is thrice the effort in magnitude, find out how efficient the machine is. [2 marks]
The given figure shows a block and tackle system of pulleys used to lift a load. When the load is pulled up by a distance 1 m, how far does the effort end moves?
8m
2m
1m
4m
