Newtons Laws Of Motion And Momentum Flashcards
Describe a perfectly elastic collision
When momentum and kinetic energy is conserved, and no energy is dissipated
What happens in inelastic collisions?
Some of the kinetic energy is converted into other forms during the collision. However, momentum is always conserved.
What are the units of impulse?
Ns
State, Newton’s first law of motion
The velocity of an object will not change, unless a net force acts upon it
State, Newton’s second law of motion in terms of momentum ( when mass is not constant) and give equation
The rate of change of momentum of the object is directly proportional to the net force which acts on the object
F= change in momentum/ change in time
And takes place in the direction of that force
Why can you not use force equals mass times acceleration when the object is accelerating close to the speed of light
Because the mass of the object will change
State Newton’s third law
If an object, A exerts a force on object, B then object B will exert an equal and opposite force on objectA
How can we reduce the impact of the force without changing momentum or speed?
We can increase the time the impact takes
What are crumple zones and what do they do?
Crumple zones are areas at the front and rear of a car that are designed to crumple on impact
They absorb some of the cars kinetic energy when they deform, which would otherwise be transferred to the passengers or the other object in the collision
They increase the time taken for the car to slow down. This intern reduces the forces acting on the passengers and whatever the car has hit.
What are airbags and what do they do?
Airbags are cushions in the dashboard and elsewhere that inflate very quickly on collisions. This makes the passengers slow down gradually, therefore increasing the
And also stop passengers from hitting the dashboard et cetera
How are seatbelts designed to protect passengers?
Seatbelts are designed to be stretched slightly, however, they still hold the passenger in place in the car, stopping them from being thrown from their seats. They absorb some of the passengers kinetic energy by stretching, and they increase the time for the passenger to come to a stop.
A spacecraft travels through space and the engine is used to accelerate the spacecraft to a given velocity the engine is then switched off. the force of gravity acting on the spacecraft is negligible state, and explain the motion of the spacecraft after the engine is switched off
Space is a vacuum therefore, there is no resistant forces acting on the spacecraft. This means there is no net force. Therefore the spacecraft will continue to travel in the same direction at constant velocity.
What is a spacecraft is travelling through space at constant velocity, the probe and the engine separate the probe objects, the engine backwards, describe and explain how the probes motion is affected by ejecting the engine
The engine exert a force onto the probe and the probe exerts an equal and opposite force onto the engine
Therefore, the probe will accelerate forward as the engine is ejected
Before a probe hit the surface of a planet, it inflates airbags describe how these airbags reduce the damage sustained by the probe as it strikes the planets surface
The airbag increases the length of time over which the momentum changes during impact
Therefore, the maximum force experienced by the probe will decrease as changing momentum equals four times changing time .
What is the area under a force time graph equal to?
It is equal to the impulse and therefore equal to the change in momentum
When a tennis player hits a ball, they continue to swing their racket. After the initial moment of contact, explain how this motion can allow a player to hit a faster shot than if they were to stop their stroke immediately after the moment of contact.
The time of contact between the board and the racket increases and as imposter equals force times time the impulse will also increase as the contact time increases.
As impulse equals the change in momentum , the momentum will also increase, so the ball will leave the racket at a greater speed as momentum is proportional to speed
Name the object that experiences a force of magnitude W, but in the opposite direction to W
Earth
According to a student, the normal contact force will equal the weight of an object when the object is stationary state why this is incorrect
Because the forces are not the same type
Give the two equations for impulse
Impulse= Mv
Impulse= rate of change of momentum
How do we find the change in velocity or momentum?
Final minus initial
Object an object collide using newtons third law of motion explain the relationship between impulse experienced by A and the impulse experience by B during the collision
A will exert an equal opposite force onto B vice versa therefore the impulse experience by a is equal opposite to the impulse experience by B however the time of contact is equal for both a and B as impulse equals the rate of change of momentum
States of principle of conservation of linear momentum
Total momentum is conserved for a closed system
Explain what is meant by an inelastic collision
There is some loss of kinetic energy during the collision
