Important questions
1. write the three equations of motion.
2. in which condition distance and displacement are equal?
3. is acceleration scalar or vector?
4. what is the difference between mass and weight?
5. what is the difference between 'g' and 'g'?
6. why can't you feel an attraction force between you and your friend?
7. uniform circular motion is accelerated motion why?
8. what is the weight of a person in the surface of moon?
9. a ship is moving at a speed of 56km/h. one second later, it is moving at 58km/h. what is its
acceleration?
10. what is the area under velocity-time graph gives?
11. explain the use of seat belt in car.
12. why the school bags have wide strap?
13. camel can easily walk through the desert. why?
14. draw the following displacement-time graphs represent cases
a. stationary object
b. uniform motion
c. no uniform motion
15. draw the following speed-time graphs represent cases
a constant speed
b. speed decreasing uniformly
c. speed increasing uniformly

1)   v = u + at

     s = ut + 1/2 at²

     v² = u² + 2as

2) The distance is equal to the displacement when their magnitude is the same.

3) Acceleration is a vector quantity

4) Mass is the quantity of matter present in a body. Its SI unit is Kg. The weight is the action of gravitational force on the body. Its SI unit is newton.

5)  G - Universal gravitational constant (6.673 x 10⁻¹¹ Nm²Kg⁻²

     g - acceleration due to gravity (9.8 m/s²)

6) It is because the magnitude of the attractive force between two people is negligible when compared with the gravitational force of Earth.

7) In a uniform circular motion, the body is continuously changing its direction. If there is a change in the direction there is an act of force acting on the body. It will in accelerated motion.

8) Due to the lesser gravitational force of the moon, the weight of the person on the moon is very low compared with the weight of the person on Earth. On the surface of the moon, the person will experience only 16.5% of his weight on the Earth.

9) The rate of change of velocity by time gives acceleration. Therefore the acceleration of the ship is when the velocity is converted to m/s

                                       a = (16.11 - 15.56)/1

                                        a = 0.55 m/s²

10) The area is equal to the displacement

11) The seat belt stops the movement of a body where newton's first law is applicable.

12) The pressure acting on a body is inversely proportional to the surface area. So, when the surface area is the increased impact of pressure on the shoulders can be minimized. So, the schoolbags have wider straps.

13) The camels have broader toe compared to the toe of the horse. So, it can walk easily through the sands.

photocells convert light energy to electricity