Two Marks Questions with Answers

Two Marks Questions with Answers

Q.1 

Explain the difference between kinematics and kinetics.

Ans. : 

In kinematics, the motion is studied without considering the forces acting on the object. In kinetics, the forces acting on the object are considered to find acceleration.

Q.2 

State the four variables used in kinematics of rectilinear motion of particles. 

Ans. : 

The four variables used in kinematics of rectilinear motion of particles are time, position, velocity and acceleration.

Q.3 

State the three equations for rectilinear motion of particles with uniform acceleration.

Ans. : 

Q.4

What are motion diagrams ?

Ans. : 

Motion diagrams are graphs involving any two of the four variables used in kinematics of rectilinear motion of particles.

Q.5 

What does area under a-t graph give ?

Ans. : 

Area under a-t graph gives change in velocity.

Q.6

What is D'Alembert's principle?

Ans. : 

According to D'Alembert's principle of dynamic equilibrium, the net external force acting on a body is balanced by the inertia force.

Q.7

What does area under v-t graph give?

Ans. : 

Area under v-t graph gives displacement.

Q.8

What does slope of tangent to v-t graph give ? 

Ans. : 

Slope of tangent to v-t graph gives acceleration.

Q.9

What does slope of tangent to x-t graph give ? 

Ans. : 

Slope of tangent to x-t graph gives velocity.

Q.10 

State the principle of work and energy.

Ans. : 

According to the principle of work and energy, the final kinetic energy of a particle can be obtained by adding the work done by all forces acting on the object to its initial kinetic energy.

Q.11

Define power.

Ans. : 

The rate at which work is done is known as power.

Q.12

What are conservative forces?

Ans. : 

If the work done by a force is independent of the path taken, the forces are said to be conservative.

Q.13 

State the law of conservation of energy.

Ans. : 

Under the action of only conservative forces, the sum of kinetic energy and potential energy of a particle remains constant.

Q.14

What is linear momentum ?

Ans. : 

Linear momentum is the product of mass and velocity of the object.

Q.15 

Define line of impact.

Ans. : 

The common normal to the surfaces in contact during the impact is known as line of impact.

Q.16

Define coefficient of restitution.

Ans. : 

The negative ratio of relative velocity after impact to relative velocity before impact is known as coefficient of restitution.

Q.17

State the values of coefficient of restitution for plastic and perfectly elastic impacts.

Ans. : 

For plastic impact, e = 0.

For perfectly elastic impact, e = 1.

Q.18 

Define impulse.

Ans. : 

The product of force and the time for which it acts is known as impulse.

Q.19

State impulse momentum theorem.

Ans. : 

According to impulse-momentum theorem, the change in momentum of a body equals the total impulse due to all forces acting on it.

Q.20

What is angular momentum ?

Ans. : 

It is product of mass moment of inertia and angular velocity.

Q.21

Give the equation of work energy for a rectilinear motion. 

Ans. : 

Work energy principle is,

KE1 + GPE1 + SPE1 = KE2 + GPE2 + SPE2

Q.22

Equation of motion of a body is s = 5t3+4t3+3t+2. Find velocity and acceleration.

Ans. : 

Q.23 

Define instantaneous velocity.

Ans. : 

The instantaneous velocity referred as velocity is given by instantaneous velocity

Q.24

What happens if two perfectly elasticbodies are in impact ?

Ans. : 

If two prefectly elastic bodies are in impact then kinetic energy and momentum are conserved and e = 1.

Q.25

What is dynamic equilibrium ?

Ans. : 

It is an equilibrium (zero net force) with some constant or uniform speed. Also, for dynamic equilibrium the forces acting are in balance.

Q.26 

What is impulsive force?

Ans. : 

The force that two colliding bodies exert on one another acts only for a short time is called as impulsive force. It is a large force acting for a small period of time on body.

Q.27 

Write the Newton's law of motion for downward motion.

Ans. : 

i) Newton's first law: Every body tries to be in its state of rest or of uniform motion along a straight line unless it is acted upon by an external unbalanced force. 

ii) Newton's second law: The rate of change of momentum of a body is directly proportional to the force acting on it and takes place in the direction of the force. 

iii) Newton's third law: Every action has equal and opposite reaction.

Q.28

a) Carom board players employ _____________ principle while playing. 

b) Snow bowling game employs ______________ principle. 

Ans. : 

a) Impulse-momentum 

b) Work-energy

Q.29

A motorist is travelling at 90 kmph, when he observes a traffic light_250 m ahead of him turns red. The traffic light is timed to stay red for 12 sec. If the motorist wishes to pass the light without stopping, just as it turns green, determine

a) The required uniform deceleration of the motor and 

b) The speed of the motor as it passes the traffic light.

Ans. : 

Q.30

Distinguish between rectilinear motion and curvilinear motion.

Ans. : 

Motion of a particle along a straight line is known as rectilinear motion whereas its motion along any curved path is known as curvilinear motion.

Q.31 

What is the direction of velocity of a particle moving along curved path ? 

Ans. : 

The velocity of a particle moving along a curved path is always directed along the tangent to the curve.

Q.32

What type of path does a projectile follow ?

Ans. : 

Projectile follows a parabolic path.

Q.33

What is time of flight?

Ans. : 

The time for which a projectile travels is known as its time of flight.

Q.34

What must be the angle of projection so that the projectile covers the maximum horizontal distance.

Ans. : 

The angle of projection must 45° for it to cover maximum horizontal distance. 

Q.35

What is banking of roads?

Ans. : 

Raising of the outer edge of a curved road above its inner edge is known as banking.

Q.36 

What are the two problems faced by vehicles moving on curved roads ?

Ans. : 

The vehicles moving on curved roads may either skid or overturn at high velocities.

Q.37

Determine the smallest radius that should be used for a highway if the normal component of the acceleration of a car traveling at 54 km/h is not to exceed 1m/s2.

Ans. : 

Q.38

What are the conditions under which the motion of a projectile is parabolic?

Ans. : 

Conditions for projectile motion to be parabolic are:

i) There should be no acceleration along the horizontal direction.

ii) Acceleration must be constant along vertical direction.