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GSEB Solutions for Class 7 Science and Technology – Lever

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):

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-11-1(b)
It is very difficult to push a heavy stone by applying physical force.

Exercise 12:

Solution 1(a):

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-12-1(a)

It is easier to push the same heavy stone using a rod and requires less effort.

Exercise 13:

Solution 1(a):

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-13-1(a)

When a 100 g mass is hanged from marking10, the wooden scale tilts.

Solution 1(b):

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-13-1(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):

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-16-1(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:

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-17-2

Solution 3:

It is a lever of the first type.

Solution 4:

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-17-4

The load is at the centre.

Solution 5:

It is a lever of the second type.

Exercise 18:

Solution 6:

GSEB Solutions for Class 7 Science and Technology - Lever-Ex-18-6

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.

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