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NEWTONS FIRST LAW OF MOTION

If an object is at rest it will remain at rest If an object is in motion it will continue to move with the same speed and direction unless no resultant force acts on it. If the resultant force is non zero or unbalance the object will move or change speed or direction.

MOMENTS

It is the turning effect of force. MOMENT =. Force. X Perpendicular distance from the pivot Nm   =    Nxm Greater distance from the pivot increases the moment or the turning effort so a small effor can lift a heavy load.

MOMENT QUESTIONS

Moment = Force X distance = 30 X 10 = 300 Nm Q2 The moment of a spanner is 50 Nm. Calculate the force acting at a distance of 10m from the pivot.

LEVERS AND GEARS

Simple Lever and Force Multipliers In all these levers, the turning effect of force is greater by increasing the distance of effort further away from the pivot. It increases the turning effect and multiply the force with a small effort. Banner 5

GEARS

GEARS TRANSMIT TURNING EFFECT OF FORCE

• Gear A Connected to the engine
• Smaller radius

GearB

• Bigger radius
• Connected to Wheels

At the Point of Contact they exert equal and opposite force. Turning effect is greater due  to greater radius .

Low gear

• Low speed and high turning effect
• small gear wheel run a bigger gear wheel
• bigger wheel has greater turning effect but slow speed

High Gear

• High speed and low turning effect
• large gear wheel run a smaller gear wheel
• small gear wheel force acts near to the shaft it run faster with a high speed but lower turning effect

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MOMENTS AND EQUILBRIUM

The sum of clockwise moments= The sum of anticlockwise moments Banner 7

WEIGHT OF THE BEAM

CENTRE OF MASS

It is the point at which the entire mass of the object can be thought as being concentrated. CENTRE OF MASS FOR SYMMETRIC OBJECTS

• It is along the point of symmetry
• If there more line of symmetry the centre of mass is at the intersection of lines of symmetry

SUSPENDED OBJECT

• The center of mass is directly below the point of suspension.
• When suspended, the weight will give the turning effect and it will come back to its equilbrium position

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SPEED, VELOCITY AND ACCELERATION

Q1 A car is travelling at the speed of 20 m/s. Calculate the distance covered in 10 minutes

DISTANCE TIME GRAPHS

VELOCITY TIME GRAPHS

SLOPE OF VELOCITY TIME GRAPH= ACCELERATION

AREA UNDER THE GRAPH = DISTANCE Banner 9

EQUATIONS OF MOTION

NEWTONS SECOND LAW OF MOTION

The acceleration of a body is a) directly proportional to the resultant force b) inversely proportional to the mass of an object

NEWTONS SECOND LAW OF MOTION

F = Mass x acceleration

SPEED UP

• The velocity of the object increases.
• The object accelerated.
• The resultant force is in the direction of motion.

SPEED DOWN

• The velocity of the object decreases .
• The object is decelerated.
• The resultant force is opposite to the direction of motion.

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WEIGHT AND TERMINAL VELOCITY

Weight (N) =  Mass (Kg) x GRAVITATIONAL FIELD STRENGTH (N/Kg) g on earth  = 9.8 N/Kg or  10 N/Kg

FORCE AND WORK RELATIONSHIP

Q1 Calculate the work done when the force of 100 N moves the object to a distance of 2m ? W =F x S = 100 x 2 = 200J Q2 Calculate the force applied when 100 J of work is done to move an object to a distance of 5 m ?

TERMINAL VELOCITY

It is the constant velocity of an object when the resultant force is zero and the weight of the body is balanced by the drag and body has zero acceleration. Terminal Velocity

TERMINAL VELOCITY IN FLUIDS

• In fluids, weight of the object is balanced by frictional force acting upwards.
• The body falls with constant velocity as net force or resultant force acting on the object is zero, so the body falls at constant velocity called the terminal velocity.

FORCES AND BREAKING

STOPPING DISTANCE

• The shortest distance a vehicle can safely stop in.
• It is the sum of thinking distance and braking distance.

THINKING DISTANCE

The distance travelled by the body during its reaction time. = Speed x reaction time Affected by tiredness, drug, alcohols as all these affects the reaction time.

BRAKING DISTANCE

• Distance travelled by the body when the braking force is applied.
• Poor weather conditions, road conditions, poorly maintained vehicles, speed of the vehicle and the mass of the vehicle affects the same.

MOMENTUM

Principle of conservation of momentum

• Momentum is a vector quantity .
• It has a magnitude as well as direction.
• Greater the speed, greater the momentum.
• Higher the velocity, higher the momentum.

CONSERVATION OF MOMENTUM

IMPACT FORCES

Relationship between force and momentum If we increase the time and the momentum is conserved, the impact force can be decreased. So greater impact time = reduced impact force

CAR SAFETY FEATURES

All these features increases the impact time, decreasing the momentum and thus reduced the impact force.

FORCES AND ELASTICITY

Effect of force on elastic objects:- Change shape or deformation by

• Bending
• Stretching
• Compressing

Elastic Deformation

Object regains its original shape when the force is removed like stretched rubber band.

Inelastic Deformation

Object that does not gain its original shape and changes shape permanently. Example: overly stretched rubber. Banner 11

FORCES AND ELASTICITY

HOOKE’s LAW

Force on a spring is directly proportional to the extension until it reaches its limit of proportionality.

FORCES AND ELASTICITY

SPRING CONTSTANT It is the measure of the stiffness of the spring. Greater the spring constant stiffer is the object. LIMIT OF PROPORTIONALITY It is the point upto which the springs obeys Hooke’s law. Beyond this point, the object comes in the plastic region and no longer obeys the Hooke’s law. Q1 Calculate the force applied on the spring when it is extended by 2m. The spring constant is 5N/m F  =  k e =5 x  2 =10 N Q2 Calculate the spring constant of a spring when a force of 50N extends the spring by 5 m. K  F/e =50/2 =10 N/m ELASTIC POTENTIAL ENERGY E =1/2 k e 2 E = Elastic potential energy (J) K = spring constant (N/m) e= extention in the spring (m) Elastic potential energy is the energy stored in the spring when it is stretched or compressed.

PRESSURE

• Greater the force greater the pressure .
• Smaller the area more will be the pressure exerted.

PRESSURE IN LIQUIDS

ATMOSPHERIC PRESSURE

• Atmospheric pressure arises due to collission of the airparticles with the Earth’s surface.
• It decreases with altitude as the number of particles decreases with height causing decrease in weight.

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KEY TERMS

b) Scalar :-Quantity that has magnitude only. eg Length, Area, Volume etc . c) Vector : Quantity that has magnitude as well as direction. eg Displacement, velocity, acceleration, momentum. d) Friction :Friction is a contact force that opposed motion between the two surfaces that are in physical contact. e) Newton First Law of Motion :-If an object is at rest it will remain at rest If an object is in motion it will continue to move with the same speed and direction unless no resultant force acts on it. f) Newton Second Law of Motion:- The acceleration of a body is a) directly proportional to the resultant force b) inversely proportional to the mass of an object. g) Newton Third Law of Motion:-For an every action force, there is an equal and opposite reaction force. h) Resultant Force It is the total force that acts on the body. It is the sum of all the forces that acts on the body .The resultant force decides the speed and the direction of the body. i) Free Body digrams are the graphical illustration to represent all the forces acting on a body. j) Moments: It is the turning effect of force. It is calculated by force multiplied by the perpendicular distance from the pivot. k) Levers : In all these levers, the turning effect of force is greater by increasing the distance of effort further away from the pivot. It increases the turning effect and multiply the force with a small effort. l) Gears : GEARS TRANSMIT TURNING EFFECT OF FORCE. m)Centre of Mass: It is the point at which the entire mass of the object can be thought as being concentrated. n) Speed: It is the distance travelled divided by the time taken. o) Velocity: Speed in a given direction. p) Acceleration: It is the change in speed over time taken. q)Weight: It is the force acting on the body due to gravity. r) Terminal Velocity: It is the constant velocity of an object when the resultant force is zero and the weight of the body is balanced by the drag and body has zero acceleration. s) Thinking Distance: The distance travelled by the body during its reaction time. t) Breaking Distance: Distance travelled by the body when the braking force is applied. u)Momentum: It is the product of mass and velocity. v) Conservation of Momentum: In a closed system, the momentum before the collission and after the collission remains unchanged. w) Hooke’s Law: Force on a spring is directly proportional to the extension until it reaches its limit of proportionality. Banner 12 Disclaimer: I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize Wikipedia Wikimedia Commons Image Source: Wikipedia Wikimedia Commons Flickr Pixabay