8th Grade Physics | Study Guide

University:
Virtual High School
Course:
STEM | Physics
Academic year:

2022
Views:

22

Pages:

3
Author:

Fachtitelb00

Physics Forces and Newton’s Laws: Newton’s Laws First Law: Objects at rest remain at rest and objects that are in motion remain in motion in a straight line unless acted upon by an unbalanced force. This law is called the law of inertia. ❖ EX: It’s harder to start pedaling a bicycle than to keep pedaling when it is already in motion. That is because objects in motion tend to stay in motion. Inertia must be overcome for the bike to start moving since things don’t spontaneously stop or start moving. Second Law: The acceleration of an object depends on the net force acting upon the object and the mass of the object. The more mass an object has, the more force it takes to increase its acceleration. ❖ FORCE = MASS TIMES ACCELERATION ❖ EX: When you are carrying a backpack while riding your bike, it will take more force to keep biking than riding without the backpack. Third Law: For every action, there is an equal and opposite reaction. ❖ EX: This is the reason a bike goes forward when you pedal it. As the wheels turn clockwise, they pass along the ground and “grip” it pushing it backward. Since every force has an equal and opposite reaction, the reaction to this force is a “push” from the ground onto the wheels of the bicycle of equal magnitude, which propels the bicycle. Forces ❖ Force: a push or pull upon an object ❖ Balanced Force: when forces on an object are of equal magnitude and in opposite directions; no acceleration ❖ Unbalanced Force: when forces on an object do not cancel out; causes acceleration ❖ Net Force: the sum of all the forces acting on an object ❖ Friction: a force that opposes motion between two surfaces that are in contact ❖ Interia: the tendency of an object to resist a change in motion unless an outside force acts on it ❖ Gravitational Force: the attractive force existing between any two objects that have mass ❖ Mass: The amount of matter in an object ❖ Weight: the measure of the force of gravity on an object Speed, Velocity, and Acceleration: Speed ❖ The rate (i.e., how fast) an object is moving is called speed. ❖ Speed is how far something travels (distance) in a given amount of time. ❖ The formula for finding speed is: ➢ SPEED = DISTANCE ÷ TIME Image: https://www.open.edu/openlearn/ocw/mod/oucontent/view.php?id=85547§ion=3.3 ❖ The unit for speed is meters or kilometers (distance) and seconds or hours (time) ➢ m/sec or km/hr Velocity ❖ Velocity used when referring to speed and direction. ➢ EX: the car is traveling at 50 km/hr north ❖ Velocity is a vector quantity ➢ Vectors can be used to show the direction and magnitude of an object’s motion Image: https://serpmedia.org/scigen/e1.6.html Acceleration ❖ When an unbalanced force is applied to a moving object, the object can accelerate by speeding up, slowing down, coming to a stop, or changing direction ❖ Any change in motion is called an acceleration ❖ Measured meters per second per second (m/sec/sec or m/sec2)