- Introduction
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- Force
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- Newton's First law of Motion
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- Inertia and Mass
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- Newton's second law of motion
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- Newton's third law of motion
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- Applying Newton's law of motion
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- Inertial frame of Reference
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- Fictitious Forces
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- Solved Examples

(a) Direction of motion

(b) Momentum

(c) Kinetic energy

(d) All the above

A Rate of change of momentum corresponds to force

B Rate of change of momentum corresponds to Kinetic Energy

Which of the following is correct

(a) A only

(b) B only

(c) Both A and B are correct

(d) Both A and B are wrong

F=dp/dt so a is correct

(a) Distance traveled by truck is shorter then car before coming to rest

(b) Distance traveled by car is shorter then truck before coming to rest

(c) Distance traveled depends on individual velocity of both the vehicles

(d) Both will travel same distance before coming to rest

By work energy theorem we know

KE

So in this case

Initial KE=retarting force * distance traveled

Since kinetic energy is same and retarding force is equal

Distance traveled will be same

(a) Both blocks will reach ground at same time

(b) Both blocks will reach ground with the same speed

(c) speed of both the blocks when they reach ground will depend on their masses

(d) Block A reaches ground before block B

since velocity of block when it reaches the ground is given by v=(2gh)

a.A child revolving in the merry ground

b. A driver in a train moving with constant velocity v

c. A passenger in a bus which is slowing down to a stop

d None of these

Since centripetal acceleration is present in merry round it is non inertial frame of reference

Since bus is slowing down to a stop,it means it is experiencing a retardation ,so it is non inertial frame of reference

A Newtons first law in valid from the pilot in an aircraft which is taking off

B Newtons first law in valid from the observer in a train moving with constant velocity

Which of the following is correct

(a) A only

(b) B only

(c) Both A and B are correct

(d) Both A and B are wrong

We know that Newtons law is invalid in Non inertial frame of reference, now since acceleration is present in Ist case..So answer is B

a. (M+m)g and R

b. R

c. R

d Mg and R

Action reaction pair acts on different body and always are in opposite direction.We will have to draw free body diagram for each part in this case.

a. The acceleration of a moving particle is always in the direction of its velocity

b. Velocity and acceleration vectors of a moving particle may have any angle between 0 and 360 between them

c.Velocity and acceleration vectors of a moving particle may have any angle between 0 and 180 between them

d. If the acceleration vector is always perpendicular to the velocity vector of a moving particle, the velocity vector does not change

In circular motion, acceleration vector is perpendicular to velocity and velocity is also changing.

Now acceleration and velocity can have any angle between

A Newtons first law in valid from the pilot in an aircraft which is taking off

B Newtons first law in valid from the observer in a train moving with constant velocity

Which of the following is correct

(a) A only

(b) B only

(c) Both A and B are correct

(d) Both A and B are wrong

when the plane is taking off, it has acceleration so it can not be intertial frame of refrence

When the observer is train moving with constant velocity, so no acceleration is involved.So it is Inertial frame.Hence Newton law is valid

a. 5 sec

b. 80 sec

c. 20 sec

d. 40 sec

Force=-(i+5j) N

Mass =5 Kg

intial velocity u=30i+40j m/sec

Acceleration:-

a=F/m=-(i+5j)/5=-.2i-j

Y component of intial velocity is 40 m/s

Acceleration in that direction -1 m/s

So

v=u+at

0=40-1t

or t=40 sec

Hence d is correct

a. velocity is constant

b. acceleration is constant

c. KE is constant

d. Particle moves in a circular path

Since force is always perpendicular to the body, work done by it will be zero

So kinetic energy is constant

It is the case of uniform circular motion

Velocity magnitude is constant but direction is constantly changing

Acceleration is constant but direction is constantly changing

Hence c and d are constant

Which of the followings is true

a.The strings stays vertical

b.The string becomes inclined to the vertical.

c.There is no force on mass m except its weight

d.The angle of inclination of the string does not depend on the v

e.The centripetal force on m is mg

Since the body is rotating on a horizontal circle,String will be inclined to the horizontal

It is shown in figure

The forces acting on the body are weight and tension in the string

Vertical component of the tension will balance out the weight of the body

Horizontal component will provide the required centripetal force for the circular motion

if T is the tension and W be the weight and θ be the angle of inclination

then

Tcosθ =Wg

And Tsinθ =mv

So angle of inclination depends on the speed of the motion

So only correct answer is b

a. going up with increasing speed

b. going down with increasing speed

c. going up with uniform speed

d. going down with uniform speed.

Since the tension is the string equals weight of the elevator,It means resultant force is zero

So acceleration must be zero

Hence c and d are correct answer

a.is an inertial frame by definition

b.cannot be inertial frame as earth is revolving around the sun

c.is an inertial frame because Newton's law are applicable in this frame

d.cannot be inertial frame because earth is rotating about its own axis

Earth cannot be inertial frame as it is revolving around the sun and also rotating about its axis

a. W(1+a/g)

b W(1-a/g)

c W

d. none of the above

Forces acting on the body

Tensile force vertically upward=S

Weight of the body vertically downward=W

Body has acceleration a vertically upwards

Net force on the body must provide the acceleration

so S-W=(W/g)a

or S=W(1+a/g)

**Confused and have questions?**

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