Q3 of 46 Page 249

A 5 N force acts on a 2.5 kg mass at rest, making it accelerate in a straight line.

(i) What is the acceleration of the mass?


(ii) How long will it take to move the mass through 20m?


(iii) Find its velocity after 3 seconds.

(i)a =

Where a is acceleration, F is force and m is mass.




(ii) According to the equations of motion,


T =


(iii) According to the equations of motion,


v = u + at


Where v is the final velocity,


u is the initial velocity,


a is the acceleration,


t is the time taken.


v = u + at


= 2×3 + 0 = 6 m/s


More from this chapter

All 46 →
2

Newton’s first law of motion gives a qualitative definition of force. Justify.

 2

The figure represents two bodies of masses 10 kg and 15 kg, moving with an initial velocity of 10 ms-1 and 5 ms-1 respectively. They collide with each other. After collision, they move with velocities 4 ms-1 and 9 ms-1 respectively. The time of collision is 2 s. Now calculate F1 and F2

 4

State the law of conservation of momentum. Two billion people jump above the earth’s surface with a speed of 4m/s from the same spot. The mass of the earth is 6x1024 kg.

The average mass of one person is 60 kg.


i) What is the total momentum of all the people?


ii) What will be the effect of this action on the earth?

 5

State Newton’s law of gravitation. Write an expression for acceleration due to gravity on the surface of the earth. If the ratio of acceleration due to gravity of two heavenly bodies is 1:4 and the ratio of their radii is 1:3, what will be the ratio of their masses?