2.2 - Newton's Laws Flashcards
What is mass? What is it measured in?
The amount of matter in an a object (kg)
What is weight? What is it measured in?
The force that acts on an object due to gravity and the objects mass (N)
What is a force?
A push or pull acting on an object due to an interaction with another object
Find the weight of a person on Earth if they have a mass of 65 kg (g = 10 N/kg)
W = m × g
= 65 kg × 10 N/kg
= 650 N
What is the gravitational field strength on the moon?
1.6 N/kg
What is the mass of a person who weighs 120 N on the Moon? (g = 1.6 N/kg)
m = W ÷ g
= 120 N ÷ 1.6 N/kg
= 75 kg
What is inertia?
A resistance to a change in motion
What is inertial mass?
A measure of how difficult it is to change a given object’s velocity
What is Newton’s first law?
A body will remain in a state of rest or in uniform motion in a straight line unless acted upon by an external resultant force
State the defining equation for Newton’s Second Law. Give appropriate units.
Resultant force (N) = Mass (kg) = Acceleration (m/s^2)
Acceleration and mass are ______ proportional. This means that if the mass of the vehicle doubles, the acceleration halves if the resultant force doesn’t change.
inversely
What will unbalanced forces cause?
acceleration
deceleration
change in direction
If an object changes direction but remains at a constant speed, is there a resultant force?
Yes , since there is a change in direction, there is a change in velocity and so there must be a resultant force.
What is resultant force
The leftover or net force when all the forces acting on the object have been combined.
What happens if there is zero resultant force?
The object will remain stationary or continue to move with a constant speed and direction.
A car weighs 1,000 kg. The resultant force is 5,000 N. What is its acceleration?
Acceleration = resultant force ÷ mass
a = 5,000 N ÷ 1,000 kg = 5 m/s
Resultant force and acceleration are _____ proportional. If the resultant force doubles, the acceleration of the vehicle also doubles if the mass of the vehicle is the same.
directly
What is the gravitational field strength on the surface of Earth?
10 N/kg
What is the approximate weight of a 1kg object on the surface of Earth?
10 Newtons
When does a falling object reach terminal velocity?
When the upwards forces (air resistance) and the downwards forces (weight) are equal to each other.
No resultant force, so constant speed.
What happens to the magnitude of air resistance on a falling object when the velocity increases?
As velocity increases, the force of air resistance on the object will also increase.
Moving through the air causes collisions with air molecules. There is friction between the moving body and the particles, which causes some of the ____ energy of the moving body to be converted into heat. Additionally, the air molecules bounce off the object gaining ___ energy.
The faster an object moves, the greater the number of collisions with air molecules. This increases ____, and the air molecules bouncing off gain even more ____ energy
Kinetic
friction
Opening the parachute provides a large surface area. This produces a huge drag force in the opposite direction to movement, slowing the skydiver down. When the parachute opens, forces become unbalanced (drag is greater than weight), and this gives a big resultant force in the opposite direction to movement, causing ______
deceleration
What is Newton’s Third Law?
Whenever two objects interact, the forces they exert on each other are equal and opposite.
Simplify Newtons 3rd Law and give an example involving a car crash.
If body A exerts a force on body B, B exerts an equal and opposite force on A. For example, if car A crashes into car B with a force of 10,000 N, then car B exerts a force of –10,000 N back on car A.
