Question

Choose the wrong statement
A. $1\,kg\,\omega t = 9.8\,N$
B. Momentum is a vector quantity
C. Force is always conserved
D. Momentum is conserved in the absence of an external force.

Answer 1

Hint: Here, we will discuss each option one by one. We know that, mass of any object is equal to the gravitational force acting on the earth. Momentum is the product of mass and velocity. Conservation of force is dependent on the type of force.

Complete answer:
Here we will discuss each step one by one to find the wrong statement.Here, in the first option, it is given that $1\,kg\,\omega t = 9.8\,N$. This statement is right, because according to Newton's law of gravitation, the mass of any object on the earth will be equal to the force of gravitation acting on earth. We know that, force of gravitation is equal to $9.8\,N$ . Therefore, we can say that $1\,kg$ of mass will be equal to the $9.8\,N$.Hence, option A is incorrect.
Now, in the second option, it is given that momentum is a vector quantity. This statement is also correct because momentum is the product of mass and the velocity. Since, velocity is a vector quantity, then the momentum will also be a vector quantity. Therefore, this option is also incorrect.
In the third option, it is given that the force is always conserved. This statement is not correct because conservation of force is dependent. Therefore, the force is not always conserved. Hence, the option C is the correct option.
Newton’s second law of motion indicates that in the absence of external force the total momentum of the entire system remains conserved. Hence, this statement is correct.Therefore, option D is incorrect.

Hence, option C is correct.

Note:A force is said to be conserved if the total energy of the system remains conserved. The force that can be conserved is known as conservative force. Therefore, the forces like gravitational force, centripetal force and spring force are conservative whereas frictional force and resistance in air are non-conservative.