**Q. What is a unit? Give an example.**

**Q. What is the necessity of selecting some units as fundamental units?**

**Q. Define the S.I. unit of solid angle.**

**Q. Define light year.**

**Q. Define a parsec.**

**Q. What is the largest practical unit of mass?**

**Q. What is lunar month?**

**Q. How many shakes are there in 1 second?**

**Q. What is a leap year?**

**Q. The farthest objects in our universe are known as quasars (quasi-stellar radio sources). Much is not known about these objects. Electromagnetic wave emitted by quasars take billions of years to reach earth. Calculate distance of a quasar from which electromagnetic wave take three billion years to reach earth.**[NCERT]

**Q. The radius of the hydrogen atom is nearly 0.5 A.What is the total atomic volume in of a mole of hydrogen atoms?**[NCERT]

**Q. The moon is observed from two diametrically opposite points and on earth. The angle**

**subtended at the moon by the two directions of observation is ‘ Given the diameter of earthto be about . Calculate the distance of the moon form the earth.**[NCERT]

**Q. The sun’s angular diameter is measured to be 1920. The distance of the sun from the earth is What is the diameter of the sun?**[NCERT]

**Q. Give examples of three physical quantities which have the same dimensions.**

**Download eSaral App for Video Lectures, Complete Revision, Study Material and much more...**

**Sol.**

**[esquestion] What is the unit of pressure if the unit of mass is**

**kg, the unit of length is metre and the unit of time is minute?**

**Q. Convert into erg.**

**Q. Calculate the value of force 100 dynes on a system based on a metre, kilogram and minute as fundamental units.**

**Q. What is a null vector?**

**Q. What are co-initial and collinear vectors?**

**Q. What is the significance of null vector?**

**Q. Can three unequal forces add upto zero?**

**Q. Under what condition the directions of sum and difference of two vectors will be same?**

**Q. Point out the essential condition for the addition of vectors.**

**Q. What is the difference between and**

**Q. Which of the following quantities are independent of the choice of orientation of the co-ordinate axes? angle between and where is a scalar?**[NCERT]

**Q. A vector has magnitude and direction. Does it have a location in space? Will two equal vectors and at different locations in space necessarily have identical physical effects?**[NCERT]

**Q. Pick out the two scalar quantities in the following list: Force, angular momentum, work, current, linear momentum, electric field, average velocity, magnetic moment, reaction as per Newton’s third law, relative velocity.**[NCERT]

**Q. Pick out only the vector quantities from the following list: Temperature, pressure, impulse, time, power, total path length, energy, gravitational potential, coefficient of friction and charge.**[NCERT]

**Q. Can you associate vectors with (i) length of a wire**

**bent into a loop (ii) a plane area (iii) a sphere?**[NCERT]

**Q. A vector has both magnitude and direction. Does that mean anything that has magnitude and direction is necessarily a vector? The rotation of a body can be specified by the direction of the axis of rotation and the angle of rotation about the axis. Does that make any rotation a vector?**[NCERT]

**Q. The position of a particle is given by $\left.3.0 t \hat{i}+2.0 t^{2} \hat{j}+5.0 \hat{k}\right)$**[NCERT]