# Center of mass and torque test for class 11

This article is about Center of mass and torque test for class 11 physics. These are very short answer type and derivation type questions for your exams. Practice them for good marks in your exams. For notes on these topics please click the links given below
Center of mass
Torque and rotational mechanics

## Center of mass and torque test

Question 1 Write the expression for the position vector of the center of mass of n-particle system.

Question 2 Discus the motion of center of mass of the decay of radio-active nucleus into two parts.

Question 3 (a) Define the term torque (with the help of labeled diagram) . Give its units and dimensional formula. Show that it is product of force and its lever arm.

(b) State and explain the principle of moments of rotational equilibrium.

Question 4 Obtain expression for the work done by torque. Hence write the expression for power delivered by a torque.

Question 5 (a) Prove that the angular momentum of a particle is equal to twice the product of its mass and areal velocity.

(b) How does it lead to Kepler’s second law of planetary motion.

Question 6 Show that the area of the triangle contained between the vectors $\vec a$ and $\vec b$ is one half of the magnitude of $\vec a \times \vec b$.

Question 7 Find the torque of a force $7\hat i -3\hat j -5\hat k$ about the origin which acts on a particle whose position vector is $\hat i +\hat j – \hat k$.

Question 8 Torque and work are both equal to force times distance then how do they differ.

Question 9 Why is it easier to open a tap with two fingers than with one finger.

Question 10 Why do we prefer to use a wrench of longer arm.

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https://en.wikipedia.org/wiki/Torque
Torque explained