GSEB Solutions for Class 7 Science and Technology – Lever (English Medium)
GSEB SolutionsMathsScience
Exercise 11:
Solution 1(a):
Parts used in a bicycle/ Name of the part | Simple machine |
Brake | Lever |
Wheel | Wheel and axle |
Nut-bolt | Screw |
Pedal | Wheel and axle |
Solution 1(b):
It is very difficult to push a heavy stone by applying physical force.
Exercise 12:
Solution 1(a):
It is easier to push the same heavy stone using a rod and requires less effort.
Exercise 13:
Solution 1(a):
When a 100 g mass is hanged from marking10, the wooden scale tilts.
Solution 1(b):
The wooden scale will become horizontal.
Solution 1(c):
The wooden scale becomes horizontal.
Exercise 14:
Solution 1(a):
Obs. no | Load
L (gm) |
Distance of load DL (cm) | Product of load and load distance
L X DL (gm . cm) |
Effort
E (gm) |
Distance of effort DE (cm) | Product of effort and distance of effort E X DE (gm.cm) |
1 | 200 | 10 | 200 X 10 = 2000 | 100 | 20 | 100 X 20 = 2000 |
2 | 400 | 10 | 400 X 10 = 4000 | 50 | 80 | 50 X 80 = 4000 |
3 | 400 | 20 | 8000 | 200 | 40 | 8000 |
Note: Load x Load-distance = Effort x Effort-distance
Exercise 15:
Solution 1:
Seesaw, scissors, pincers, beam balance, pliers, etc.
Solution 1(a):
Object |
Mark ‘✓ ‘ what is at centre | ||
Fulcrum | Load |
Effort |
|
Lemon-juicer | ——— | ✓ | ——— |
Scissors | ✓ | ——— | ——— |
Nut cracker | ——— | ✓ | ——— |
Fork | ——— | ——— | ——— |
Utensil plucker | ——— | ——— | ✓ |
Long handled broom | ——— | ——— | ✓ |
Plier | ✓ | ——— | ——— |
Solution 2:
Lemon squeezer, nutcracker, oar of a boat, a wheel barrow, stapler, etc.
Exercise 16:
Solution 1(a):
Solution 3:
Tongs, broom, fishing rod used by anglers, sugar tongsetc.
Exercise 17:
Solution 1(a):
Beam balance, plucker, tongs, oars, nut cracker.
Solution 1(b):
Sr. No | Name of the object | What is at the centre? | Type of lever | Use |
1. | Wheel barrow | Load | Second | To carry objects from one place to another at construction sites. |
2. | Nutcracker | Load | Second | To break nuts. |
3. | Pliers | Fulcrum | First | To cut or bend wires. |
4. | Lemon squeezer | Load | Second | To extract juice form a lemon |
5. | Fishing rod | Effort | Third | To catch fish |
6. | Scissors | Fulcrum | First | To cut paper or cloth |
Solution 1:
Dustbin
Solution 2:
Solution 3:
It is a lever of the first type.
Solution 4:
The load is at the centre.
Solution 5:
It is a lever of the second type.
Exercise 18:
Solution 6:
The load is at the centre.
Solution 7.1:
It is a lever of the first type.
Solution 7.2:
Effort: The force applied at one of the ends of the lever to do work.
Load: The object which can be pushed or lifted using one of the ends of the lever.
Fulcrum: The point with respect to which the rod can move freely.
Solution 8.1:
To cut metal sheets using scissors more force is required.
If the length of the handles are kept more, the effort-distance becomes more than the load-distance. According to the principle of a lever, work can be done with less effort if the effort-distance is more than the load-distance. Thus, to make the work of cutting a metal sheet easier using less effort, the length of the handles of the scissors used to cut the metal sheet are kept longer.
Solution 8.2:
To cut cloth, a tailor requires less force but the work has to be done quickly. If the length of blades of the tailor’s scissors, is more than that of handles, then the load-distance becomes more than effort- distance. So, when force is applied on the handles, handles move less but the blades move over a larger distance. Due to this more length of cloth is cut quickly and the speed of work also increases. Hence, the length of handles of scissors used by a tailor is less and the length of blades is more.