Identify Newton's Laws
You can push a small, empty cart and it speeds up easily, but if you load it with heavy boxes, you have to push harder to get the same increase in speed.
Newton’s Second Law (F = ma)
_____________ is a push or pull
Force
Write down the equation for Newton's 2nd Law
F = ma
Which force is always present & always act downwards
Gravity
The unit of force is
Newton (N)
When a swimmer pushes backward against the water with her arms, she is propelled forward through the pool.
Newton’s Third Law (Action-Reaction)
The tendency of an object to resist a change in motion is called _______
Inertia
A box with a mass of 10 kg accelerates with an acceleration of 6 m/s2. What is the net force on the box?
60 N
Friction
The unit of mass
Kilogram (kg)
A textbook lying motionless on a desk stays right where it is until a student gives it a push.
Newton’s First Law (Inertia)
The measure of the force of gravity on an object
Weight
Two people are playing tug-o-war with a rope. The person on the left pulls with a force of 20 N, and the person on the right pulls with a force of 35 N. What is the net force & direction of the rope?
15 N (Right)
Forces that require contact are called
Contact Forces
The unit of time is
Seconds
A passenger riding in a car that suddenly stops feels her body lurch forward before the seatbelt pulls her back.
Newton’s First Law (Inertia)
A measurement that has both magnitude & direction
Vector
A bicycle with a mass of 20 kg experiences a net force of 100 N. What is the acceleration of the bicycle?
a = F/m = 100/20 = 5 m/s^2
Forces like gravity that don't require contact & can act over a distance are called
Non-Contact (Field) Forces
The unit of distance or displacement is
When a firefighter turns on a powerful hose, the water blasts out forward, but the hose itself kicks back toward the firefighter.
Newton’s Third Law (Action-Reaction)
The amount of matter something had is _______________
Mass
A train applies a force of 10,000 N to the left and friction applies a force of 4000 N to the right, causing it to accelerate with an acceleration of 3 m/s2. What is the mass of the train?
m = F_{\text{net}}/a = 6000/3 = 2000 \ \text{kg}
The force that acts perpendicular to and is exerted by a surface is called
Normal Force
The unit of acceleration is
m/s2