newton's laws and inertia Flashcards
what is newton’s first law?
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it will continue moving at the same velocity.
what is needed to change the velocity of an object?
a resultant force
an object is moving with a 50N force to the right, and a 50N force to the left. What is the resultant force and what effect does it have on the object?
The forces are balanced so the resultant force is zero, meaning that the object will continue moving at the same velocity.
what is need for a constant speed?
a driving force and a resistive force, with the same force
a train is moving at a constant velocity, what is the relationship between the driving and resistive force?
they are balanced
what will a non-zero resultant force produce?
an acceleration or deceleration in the direction of the resultant force
what is newton’s second law?
the acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass if the object
what does newton’s second law mean?
the larger the resultant force, then the larger the acceleration
if the mass is larger, then the acceleration will be smaller
An object has a resultant force of 10N, and another has a resultant force of 20N. What is the relationship for acceleration between the two objects?
The object with a force of 20N will experience twice the acceleration of the other object.
Two objects have the same resultant force. One object has a mass of 1kg, and another has a mass of 2kg. What is the relationship for acceleration between the two objects?
The object with a mass of 1kg will experience twice the acceleration of the other object.
what is the equation linking acceleration, mass and force?
Force (N) =mass (kg) x acceleration (m/s²)
F=ma
calculate the force needed to accelerate an object with a mass of 5kg by 4m/s²
F=ma
F=5 x 4
F=20N
A force of 50N is applied to an object with a mass of 0.5kg. Calculate the acceleration of the object.
a=F/m
a=50/0.5
a=100m/s²
estimate the resultant force on a car as it accelerates from rest to a typical speed
typical speed 25m/s
takes 10s to reach this
a=v/t
a=25/10
a=2.5 m/s²
typical mass is 1000kg
F=ma
F=1000 x 2.5
F=2500N
average acceleration from a main road to a motorway
2 m/s²
average speed a car travels on a main road and a motorway
main road: 13m/s
motorway: 30 m/s
inertia
objects will stay still or keep the same motion unless you apply a resultant force
inertial mass
a measure of how difficult it is to change the velocity of an object
inertial mass equation
m=F/a
the ratio of the force needed to accelerate an object, over the acceleration produced
what is the difference between the force required to produce an acceleration for an object with a larger inertial mass compared to one with a smaller inertial mass?
the object with a larger inertial mass will require a larger force
what is newton’s third law?
when two objects interact, the forces they exert on each other are equal and opposite
give three examples of newton’s third law
- canoeing-The paddle pushes onto the water. At the same time the water pushes back on the paddle. This force is equal in magnitude but opposite in direction.
- rocket-When a rocket fires, the chemical reaction produces a downward push force on the hot exhaust gases. The exhaust gases exert an equal force on the rocket but acting in the opposite direction.
- a book on a table in equilibrium-the normal contact force from the table is pushing up on the book and the normal contact force from the book is pushing down on the table
