Q.No.99: - Under what condition instantaneous velocity and average velocity of a body becomes equal?

Q.No.99: - Under what condition instantaneous velocity and average velocity of a body becomes equal?

Ans: - If a body moves with uniform velocity then the instantaneous velocity and average velocity of a body becomes equal.

Q.No.98: - What is meant by variable acceleration?

Q.No.98: - What is meant by variable acceleration?

Ans: - If the change in velocity is not equal in equal interval of time then the body will accelerate with variable acceleration.

Q.No.97: - State Newton’s third law.

Q.No.97: - State Newton’s third law.

Ans: - Action and reaction are equal in magnitude but opposite in direction.

Q.No.95: - Find unit of force from Newton’s second law.

Q.No.95: - Find unit of force from Newton’s second law.

Ans: -                      F=ma      (Newton’s law)

                               F=kgms^-2

               So,           F= kgms^-2     =     N 

kgms^-2 is called Newton read as ‘N’ so we can say kgms^-2 and ‘N’ are the units of force.

Q.No.94: - State Newton second law.

Q.No.94: - State Newton second law.

Ans: - A force applied on a body produces acceleration in its own direction. The acceleration produced is directly proportional to the applied force and inversely proportional to the mass of the body.

Q.No.93: - If we increase the force then acceleration increase and if we increase the mass then acceleration decrease. Drive the mathematical relation between force, mass and acceleration according to this statement.

Q.No.93: - If we increase the force then acceleration increase and if we increase the mass then acceleration decrease. Drive the mathematical relation between force, mass and acceleration according to this statement.

Ans: - Mathematically,

Q.No.92: - What happens if we increase the mass of the body which is moving with some positive acceleration? What result will you get from it?

Q.No.92: - What happens if we increase the mass of the body which is moving with some positive acceleration? What result will you get from it?

Ans: - If is experimental fact that if we increase the mass of the body then its acceleration will decrease. So, we can say that mass and acceleration are inversely proportional to each other.

Q.No.91: - What happens with the velocity of body if an unbalanced external force exert on the body?

Q.No.91: - What happens with the velocity of body if an unbalanced external force exert on the body?

Ans: - An unbalanced external force always changes the velocity and thus the body will accelerate.

Q.No.91: - What happens with the velocity of body if an unbalanced external force exert on the body?

Q.No.91: - What happens with the velocity of body if an unbalanced external force exert on the body?

Ans: - An unbalanced external force always changes the velocity and thus the body will accelerate.

Q.No.90: - How can we increase or decrease the inertia of a body?

Q.No.90: - How can we increase or decrease the inertia of a body?

Ans: - Simply by increasing or decreasing the mass of body we can change the body’s inertia.

Q.No.89: - Define inertia.

Q.No.89: - Define inertia.

Ans: - The property of an object that tends to maintain the state of rest or state of uniform motion is known as object’s inertia.

Q.No.89: - Define inertia.

Q.No.89: - Define inertia.

Ans: - The property of an object that tends to maintain the state of rest or state of uniform motion is known as object’s inertia.

Q.No.88: - State Newton’s first law.

Q.No.88: - State Newton’s first law.

Ans: - A body at rest will remain at rest and a body moving with uniform velocity will continue to do so unless acted on by some unbalanced external force.

Q.No.87: - Which laws are valid in inertial frame of reference?

Q.No.87: - Which laws are valid in inertial frame of reference?

Ans: - Newton’s laws are valid in the inertial frame of reference.

Q.No.86: - Differentiate inertial and non-inertial frame of reference.

Q.No.86: - Differentiate inertial and non-inertial frame of reference.

Ans: - “A frame of reference which is not being accelerated and it may be at rest or moving with uniform velocity is called inertial frame of reference” while such a frame of reference which has non-uniform motion but certain acceleration is called non-inertial frame of reference.

Q.No.85: - What is frame of reference?

Q.No.85: - What is frame of reference?

Ans: - A set of reference axis required to locate the position of an object in space is called a frame of reference.

Q.No.84: - Do objects of different weights fall with the same acceleration on the earth?

Q.No.84: - Do objects of different weights fall with the same acceleration on the earth?

Ans: - Yes, objects fall with the same acceleration regardless of their weights at the surface of earth in situations air friction is negligible.

Q.No.83: - Why the direction of acceleration due to gravity ‘g’ is always downward? Explain with example.

Q.No.83: - Why the direction of acceleration due to gravity ‘g’ is always downward? Explain with example.

Ans: - The gravitational acceleration depends upon the change in direction and ∆v is always downward so ‘g’ is always downward.

Example: - Let us take an example, if we through a ball upward straight with velocity 10ms^-1 after some time its velocity will decrease and we take it

8ms^-1 (for simplicity) so it’s Vi = 10ms^-1 and Vf = 8ms^-1 and

                                             ∆v=Vf-Vi

                                             ∆v=8ms^-1 – 10ms^-1

                                             ∆v=–2ms^-1

∆v have –ve sign which is opposite to its motion which means downward now we take the second trip when body starts moving downward at highest point its velocity will be zero ”0” after some time its velocity will increase and we take 2ms^-1 (for simplicity) so its Vi=0 and Vf=2ms^-1 and,

                                              ∆v=Vf-Vi

                                             ∆v=2ms^-1 – 0ms^-1

                                             ∆v=–2ms^-1

 The ∆v is positive which means that gravitational acceleration will be along the direction of motion means again downward direction. Hence, ∆v is always downward so ‘g’ is always downward.        

Q.No.82: - Write down the basic three equation of linear motion.

Q.No.82: - Write down the basic three equation of linear motion.

Ans: -

                           V_f    =    V_i   +   at

                            S    =     V_it + at²

                         2aS   =     V_f² – V_i²

Q.No.81: - If the body is moving with uniform linear velocity in magnitude but its direction is changing then it will have acceleration. Can we check this type of acceleration from v-t graph? If not then why?

Q.No.81: - If the body is moving with uniform linear velocity in magnitude but its direction is changing then it will have acceleration. Can we check this type of acceleration from v-t graph? If not then why?

Ans: - The v-t graph is drawn between the magnitudes of velocity and time. So we can’t check this type of acceleration from graph, because in this case the acceleration is produced only due to change in direction.