physics a midterm study guide - weebly
TRANSCRIPT
1. NEWTON’S LAWS OF MOTION Newton's laws predict the motion of most objects. As a basis for understanding this concept: A. Students know how to solve problems that involve constant speed and average speed.
Motion Graphs: B. Students know that when forces are balanced, no acceleration occurs; thus an object continues to move at a constant speed or stays at rest (Newton's first law).
Distance Formula: Use this formula to relate distance, speed, and time for an object that is moving at constant speed or at an average speed.
𝑥 = 𝑣 𝑡 distance velocity time [ m ] [ m/s ] [ s ]
A really easy way to visual velocity is by creating a position vs. time graph. The motion will be represented by a line on the graph, with the slope of the line being equal to the velocity.
𝑣 =∆𝑥∆𝑡
=𝑟𝑖𝑠𝑒𝑟𝑢𝑛
= 𝑥 − 𝑥!𝑡 − 𝑡!
steady
speeding up
fast, steady
rest
backwards
Distan
ce (m
)
Time (s)
acceleration (𝑎) unit: meter per second per second (m/s²)
a measure of the rate of change of velocity.
force (𝐹) unit: newton (N) a push or a pull. part of an interaction between two objects.
position (𝑥) unit: meter(m) a measure of the location of an object.
velocity (𝑣) unit: meter per second (m/s) a measure of the rate of change of position. velocity is an object’s speed and its direction. time (𝑡) unit: second (s) a measure of how much time has passed.
Change of Speed Formula Use this formula to find the change of speed
due to an acceleration.
∆𝑣 = 𝑎 𝑡 velocity change acceleration time
[ m/s ] [ m/s² ] [ s ]
The Law of Inertia: An object at rest will tend to stay at rest. An object in motion will tend to stay in motion. In other words…
Forces cause acceleration! If there is no force on an object, its velocity cannot change. It will have to be at rest or moving in a straight line path at constant speed.
Physics A Midterm Exam – Study Guide
Net force is the sum of all the forces. −4N
net 𝐹 = (−4) + (6)
6N 4N −6N
net 𝐹 = 2N
net 𝐹 = (4) + (−6)
net 𝐹 = −2N
C. Students know how to apply the law 𝑭 =𝒎𝒂 to solve one-‐dimensional motion problems that involve constant forces (Newton's second law). D. Students know that when one object exerts a force on a second object, the second object always exerts a force of equal magnitude and in the opposite direction (Newton's third law). Ex 1. A baseball player hits a baseball. ACTION: the bat pushes the baseball forward. REACTION: the baseball pushes the bat backward. Ex 2. A cannonball is fired out of a cannon. ACTION: the cannon pushes the ball forward. REACTION: the ball pushes the cannon backward.
mass (𝑚) unit: kilogram(kg) a measure of the amount of material in an object.
weight (𝑤) unit: newton(N) a measure of the gravitational force acting between two objects.
𝐹 = 𝑚 𝑎 force mass acceleration [N] [kg] [m/s²]
Newton’s 2nd Law Acceleration is directly proportional to force
and inversely proportional to mass.
Mass vs. Weight: Weight is directly proportional to mass, but it is not equal to mass. Mass is a measure of the amount of material in an object, whereas weight is a measure of the gravitational force on an object. In places with less gravity, the weight of an object will decrease, but its mass will still be the same.
Weight Formula Use this formula to calculate the weight of an object, remember on Earth 𝑔 = 10m/s².
𝑤 = 𝑚 𝑔
weight mass acceleration of gravity
[N] [kg] [m/s²]
“The force on object B from object A is equal to the force on object A from object B, but in the opposite direction.”
𝐹!" = −𝐹!" Since a force is part of an interaction between two objects, forces always come in pairs!
ACTION and REACTION
Since the two forces are equal, the object with less mass will
experience a greater acceleration.
This is the reason why the baseball goes flying, but the bat
appears to be unaffected.
action reaction
action
reaction
Since the two forces are equal, the object with less mass will
experience a greater acceleration.
This is the reason why the
cannonball goes flying, but the cannon barely moves at all.