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):

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:

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.