Chapter Chosen

Laws of Motion

Book Chosen

Physics Part I

Subject Chosen


Book Store

Download books and chapters from book store.
Currently only available for.
CBSE Gujarat Board Haryana Board

Previous Year Papers

Download the PDF Question Papers Free for off line practice and view the Solutions online.
Currently only available for.
Class 10 Class 12
Two bodies of masses 10 kg and 20 kg respectively kept on a smooth, horizontal surface are tied to the ends of a light string. A horizontal force F = 600 N is applied to
(i) A, (ii) B along the direction of string.
What is the tension in the string in each case?

Horizontal force, F = 600 N

Mass of body A, m1 = 10 kg

Mass of body B, m2 = 20 kg

Total mass of the system, m = m1 + m2 = 30 kg

Using Newton’s second law of motion,

                        F = ma 

Acceleration (
a) produced in the system can be calculated as, 

         straight a space equals space straight F over straight m = 600 over 30 space equals space 20 space m divided by s squared space

When force is applied on a body A. 

Equation of motion can be written as, 

F - T = m1a


T = F - m1a

   = 600 - 10 x 20

   = 400 N                                ...  (i)

When Force is applied on a body B, we have 

F - T = m2a

i.e., T = F - m2


T = 600 - 20 x 20 = 200 N         ... (ii)

From (i) and (ii), we can say that the answer is different in both the cases. 

Therefore, the answer depends on which end of mass, the force is applied.

State Galileo’s law of motion.

Galileo’s law of motion states that, a body continues to move in the same direction with constant speed, if no force is acting on the body. 

What is Aristotle’s law of motion?

Aristotle’s law of motion states that an external force is required to keep the body in motion.

Is Aristotle’s law of motion now correct?

No. Aristotl'e law of motion is false. 

Define inertia.

The property by virtue of which the body cannot change its state of rest or uniform motion in a straight line, unless an external force is acting on the body is called as Inertia. 

When the branches of an apple tree are shaken, the apples fall down. Why?

The apple fall from an apple tree when it shaken because of inertia of rest. Apple is in a state of rest and when the tree is suddenly shaken, apples still tends to remain in it's same state of rest whereas branches move. 

So, the apples fall down.