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Astronomy Olympiad

Problems on Dynamics

Any vector quantity can be divided into two parts.

  1. Parallel to the axis
  2. Perpendicular to the axis

Irrespective of the situation the components (parallel and perpendicular parts) can be read from the graph as follows:-


Text Box: y component
Text Box: y-axis
The y component is the perpendicular component and the x component is the parallel component. In the figure the red line indicates vector.

To calculate the net force on the body one has to add the parallel components together and the perpendicular components together. The resultant out of this is the net force acting on the body.

The Newton's laws of motion

To learn more about the forces go to:-

  1. Forces 1
  2. Forces 2
  3. Forces 3
  4. Forces 4

The Newton's laws of motion are as follows:-

1)      Law of inertia: - If a body is at rest, it will remain at rest. If the body is moving with a constant velocity, it will continue to do so.

2)      The force acting on the body is equal to the rate of change of momentum possessed by the body.  


3)      For every action there is always equal and opposite reaction.


Q1)            Look at the following graph. What is the force acting on the body?


Q2)            Can a body moving on surface continue its motion endlessly? Why?

Q3)            What is your mass? What is the force acting on your body right now?

Q4)            Look at the following graph. What is the force acting along

a.       x-axis

b.      y-axis


Q5)            Find the net resultant force on the body in each of the following cases.

Take the scale as 1 cm =5 N on each of the axis.

Text Box: y axis
Text Box: y axis
Text Box: y axis
Text Box: y axis
Hint:- You can draw the diagrams in the note book and take the components accurately.

Q6)            A rocket moves upwards in the space with a zero initial velocity. The following is the velocity of the rocket at various times. Calculate the force acting on the rocket.

Time (hr)

Distance (km)








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