Question

pressure on the ground, the boy or the man?
(iii) Who is likely to sink into the ground, the man standing on a pointed edge or the boy
standing on one foot and why?
7. A force of 250 N, while acting on an area X produces a pressure of 1000 Pa. Calculate the magnitude
of X in cm?
8. The base of a wooden box measures 15 cm x 20 cm. It is placed on a bed. If the weight of the box is
60 N, what is the pressure exerted by the box on the bed?
9. The pressure between a jeep tyre and the road is 100000 Nm-2. If the jeep has a weight of 10000 N,
what is the area of contact between the tyre and the road?
10. Abhinav can open a door by applying a force of 6 N on a 2 m wide door. Find the moment of force
required to open the door.
11. Shiv opens a nut with the help of a spanner of length 30 cm by applying a force of 120 N. Calculate
the moment of force required to open the nut.
12. The moment of force about a fixed end A of a rod AB of length 1.5 m is 60 Nm. What is the force
applied at the free point B of the rod?
57
10. The​

Answer 1

Answer:

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Solution 1

Value of gravitational constant G on the earth and the moon is = 6.67 x 10-11Nm2/kg2

Note that the value of G always remains constant irrespective of the location.

Question 2

Which force is responsible for the moon revolving round the earth?

Solution 2

Gravitational force is responsible for the moon revolving round the earth.

Question 3

Does the acceleration produced in a freely falling body depend on the mass of the body?

Solution 3

No, the acceleration produced in a freely falling body is independent of the mass of the body.

Question 4

Name the scientist who gave the three laws of planetary motion.

Solution 4

Johannes Kepler gave the three laws of planetary motion.

Question 5

Name the scientist who explained the motion of planets on the basis of gravitational force between the sun and planets.

Solution 5

Newton explained the motion of planets on the basis of gravitational force between the sun and planets.

Question 6

State the Kepler's Law which is represented by the relation .

Solution 6

Kepler's law of periods states that: The cube of the mean distance of a planet from the sun is directly proportional to the square of time it takes to move around the sun.

Question 7

Which of the Kepler's law of planetary motion led Newton to establish the inverse-square rule for gravitational force between two bodies?

Solution 7

Kepler's third law of planetary motion led Newton to establish the inverse-square rule for gravitational force between two bodies.

Question 8

Name the property of earth which is responsible for extremely small acceleration being produced in it as a result of attraction by other small objects..

Solution 8

Extremely large mass of the earth.

Question 9

What is the acceleration produced in a freely falling body of mass 10kg? (Neglect air resistance)

Solution 9

Acceleration produced in a freely falling body, irrespective of its mass, is 9.8m/s2

Question 10

When an object is dropped from a height, it accelerates and falls down. Name the force which accelerates the object.

Solution 10

Gravitational force of the earth.

Question 11

Give the formula for the gravitational force F between two bodies of masses M and m kept at a distance d from each other.

Solution 11

The gravitational force F between two bodies of masses M and m kept at a distance d from each other is :

Here, Gravitational constant, G=6.7 x10-11Nm2 kg-2

Question 12

What force is responsible for the earth revolving round the sun?

Solution 12

Gravitational force is responsible for the earth revolving round the sun.

Question 13

What name has been given to the force with which two objects lying apart attract each other?

Solution 13

Gravitational force causes two objects lying apart attract each other.

Question 14

What type of force is involved in the formation of tides in the sea?

Solution 14

Gravitational force (exerted mainly by the moon and to some extent by the sun) is involved in the formation of tides in the sea.

Question 15

Which force is responsible for holding the solar system together?

Solution 15

Gravitational force of the sun holds the solar system together.

Question 16

What is the weight of a 1kilogram mass on the earth? (g=9.8m/s2)

Solution 16

Weight, W = m x g

= 1 kg x 9.8m/s2=9.8 N

Question 17

On what factor/factors does the weight of a body depend?

Solution 17

The weight of a body is directly proportional to its mass.

It also depends on the acceleration due to gravity which varies from place to place.

Question 18

As the altitude of a body increases, do the weight and mass both vary?

Solution 18

Weight of the body varies with altitude; mass of an object is constant.

Question 19

If the same body is taken to places having different gravitational field strength, then what will vary: its weight or mass?

Solution 19

Its weight varies; mass of an object is constant.

Question 20

If the mass of an object be 10kg, what is its weight? (g=9.8m/s2)

Solution 20

M= mass of the earth.

R=radius of the earth