Force And Laws Of Motion Flashcards
What are the different effects of force?
1) force can make a stationary object move
2) force can stop a moving object
3) force can change the speed of a moving object
4) force can change the direction of the moving object
5) force can change the shape and size of an object
Is force a scalar quantity or vector quantity?
Vector quantity
State Newton’s first law of motion
It states that an object at rest will remain at rest and an object in motion will remain in motion in a straight line with uniform speed unless it is combelled by an external force to change its state of rest or of uniform motion
Newton’s first law explains which property of the body?
Inertia
On which factor inertia of a body depends?
Mass of the body
Define inertia
The natural tendency of an object to resist a change in their state of restnor of uniform motion along a straight line
What are the two factors on which the momentum of the body depends?
Mass of the body and velocity of the moving body
How is Momentum related to the mass of the body?
It is directly proportional to the mass of the body
How is Momentum related to the velocity of the moving body?
It is directly proportional to the velocity of the moving body
Define momentum
It is defined as the product of mass and velocity
Formula to find momentum
Momentum = mass×velocity
p=mv
Is momentum a scalar quantity or vector quantity?
Vector quantity
SI unit of momentum
kgm/s
Formula to find change in momentum
Final momentum- initial momentum
mv-mu
m(v-u)
State Newton’s second law of motion
It states that the rate of change of momentum is directly proportional to the applied force and takes place in the direction in which the force acts.
Define force
Force is defined as the product of mass and acceleration
F=ma
SI unit of force
Newton (N)
Define 1N
1 N is that force which when acting on a body of 1 kg produces an acceleration of 1 m/s²
When a hanging carpet is beaten with the stick the dust particles start coming out of it. give reason.
When a hanging carpet is beaten with a stick then the carpet moves to and fro slightly but the dust particles tend to remain at rest due to inertia of rest and hence the dust particles separate from the carpet and fall down
When a tree is shaken the fruits and leaves fall down, why?
When a tree is shaken the tree moves to and fro slightly but the fruits and leaves tend to remain at rest due to inertia of rest and hence get detached from the tree and fall down
Why do the passengers in a bus fall backward when it starts suddenly?
When the bus starts suddenly then the lower part of the body of the passenger in the contact with bus comes in motion but the upper part of the body remains at rest due to inertia of rest, therefore the passenger fall backward
Why do a passenger travelling in a bus fall forward when the bus stops suddenly?
When a moving bus suddenly stops then the lower part of the body in contact with bus tend to come at rest but the upper part of the body remains in motion due to inertia of motion that is why passengers travelling in a bus fall forward.
Why is it advised to tie any luggage kept on a roof of a bus with a rope?
When the bus stops suddenly the bus comes in the state of rest but the luggage remains in motion due to inertia of motion thus the luggage move forward and may fall down from the roof of the bus. If the bus starts suddenly then bus comes in the state of motion but the luggage remains in the state of rest due to inertia of rest so the luggage moves backward and may fall down from the roof of the bus therefore it is advised to tie the luggage kept on the roof of a bus with a rope.
A Karate player can break a pile of tiles with a single blow of his hand. give reason.
This is because a Karate player strikes the pile of tile with his hand very very fast. In a doing so large momentum of the hand reduces to zero in a short interval of time this exerts a very large force on the pile of tile which is sufficient to break the pile of tile.
In a cricket match a player moves his hand backward on catching a fast cricket ball. give reason.
A fast moving cricket ball has a large momentum in stopping this ball the momentum has to be reduced to zero when a cricket man moves his hands back on catching the fast ball then the time taken to reduce the momentum of a ball to zero is increased due to this the rate of change of momentum is decreased and Hence a small force is exerted on the hands of the player and the player does not get hurt.
During Athletics Meet a high jumping athlete is provided either with a cushion or a heap of sand.give reason.
When the higher jumper falls on a cushion then the jumper takes a longer time to come to stop due to which a small force acts on the athlete and the athlete does not get hurt
What is the use of seat belts in a car?
A fast moving car has a large momentum when the car meets an accident than the last momentum of the car reduces to zero in a short interval of time but just stretchable seat belt increases the time taken by the passenger to fall forward due to this longer time less force is exerted on them the passenger does not get injured
State Newton’s third law of motion
It states that to every action there is an equal and opposite reaction
What is action and reaction?
The force exerted by the first body and the second body is known as action and the force exerted by the second body and the first body is known as reaction
Is action and reaction acting on the same or different body?
Action and reaction always acts on the different bodies
How do we walk?
When we walk on the ground then our foot pushes the ground backward and in return the ground pushes our foot forward this forward reaction exerted by the ground on our foot helps us to walk.
Why is it very difficult to walk on a slippery ground?
On the slippery ground the friction is much less and we cannot exert a backward action force on the slippery ground which would produce of Forward reaction force on us
Why the gun recoils?
When a bullet is fired from a gun the force sending the bullet forward is equal to the force sending the gun backward but due to the high mass of the gun, the gun moves only a little backward producing a jerk to the shoulder of the gunman so the gun is said to have recoiled.
Explain why is it difficult for a fire man to hold a hose pipe which ejects large amount of water on a high velocity.
When a firehose pipe ejects large amount of water in the forward direction at a high velocity then a forward going stream of water exerts a backward reaction force due to which the hose pipe tend to go backward and slips from the hands of the fireman, this backward movement of hose pipe makes it difficult for a fire man to hold it.
