Vocabulary
Forces, Gravity, and Friction
Newton's 1st Law
Newton's 2nd Law
Newton's 3rd Law
100
a push or pull on an object
force
100
Give an example of a non-contact force
Gravity, magnetism, or electric force
100
Your phone sits on a table. Are the forces acting on the phone balanced or unbalanced?
Balanced
100
An object has a mass of 4 kg and accelerates at a rate of 4 m/s². What is the net force?
16 Newtons
100
A 1 kg object moves at a velocity of 5 m/s. What is its momentum?
5 kg x m/s2
200
an attractive force that exists between all objects that have mass
gravity
200
This type of friction opposes the motion of round objects (like wheels and spheres) as they move across a surface
rolling friction
200
You kick a soccer ball through the air. Are the forces acting on the soccer ball balanced or unbalanced?
Unbalanced.
200
An object experiences a net force of 20 N and has a mass of 5 kg. What is its acceleration?
4 m/s2
200
Your friend fires a firework off of the ground. The action force is diagonally upwards towards the right. What is the direction of the reaction force?
Diagonally downwards towards the left.
300
the gravitational force exerted on an object
weight
300
Gravity depends on what two variables?
Mass and distance
300
What are the two conditions in which the net force acting on an object can be zero?
1. the object isn't moving. 2. the object is moving at a constant speed in a straight line.
300
An object experiences a net force of 1000 N and accelerates at a rate of 10 m/s². What is its mass?
100 kg
300
A baseball player uses a bat to hit a baseball to the right with a force of 55 N.
a. Draw a diagram of what is happening. Identify the action and reaction forces.
b. According to Newton’s Third Law, how much force does the baseball exert on the bat, and in what direction?
A. Varies. B. 55 Newtons to the left
400
the tendency of an object to resist a change in its motion
inertia
400
Your friend Joe is 250 meters away. You walk closer to Joe such that you are now 100 meters away from him. What happened to the gravitational force between you and Joe?
It increased/strengthened.
400
What is Newton's 1st Law of Motion?
if the net force on an object is zero, the motion of the object does not change
OR
an object at rest stays at rest, and an object in motion stays in motion at a constant speed and in a straight line, unless it is acted upon by an unbalanced external force
OR
the law of inertia
400
What is Newton's 2nd Law of Motion?
the acceleration of an object is equal to the net force acting on the object divided by the object’s mass
OR
F = ma
400
What is Newton's 3rd Law of Motion?
when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object
OR
Every action has an equal and opposite reaction
500
the total momentum of a group of objects stays the same unless outside forces act on the objects
law of conservation of momentum
500
List the four types of friction in order from strongest to weakest
Static, sliding, rolling, fluid
500
A sky-diver falls through the air. Gravity pulls him downward with a force of 750 N. Air resistance opposes his fall with a force of 200 N.
a. Draw what is happening
b. What is the net force and its direction?
c. Are the forces balanced or unbalanced?
A. Varies. B. 550 N down. C. Unbalanced.
500
5 m/s2
500
A large truck traveling down the highway collides with a tiny mosquito floating in the air. The mosquito is crushed but not the truck. According to Newton's 3rd Law, both the truck and the mosquito experience the same net force from the collision. Why, then, is the mosquito crushed, but not the truck?
The mosquito is crushed not because it felt more force, but because its tiny mass causes it to accelerate violently from that force (F=ma).