8th grade Science Forces & Gravity

Flashcards by Pisgah, updated more than 1 year ago
 Created by Pisgah over 5 years ago
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study guide - 8th grade science motion & forces

Resource summary

 Question Answer What was Newton's Second Law? it describes how force, mass, and acceleration are related. What is the formula for acceleration? acceleration=force/mass a=f/m F=m*a What is Friction? The force that opposes the sliding motion of the two surfaces that are touching each other. What is the force that opposes most motion? friction How does Newton's 2nd law prove his first law? If the force is 0 that means an object at rest is staying at rest and an object that is moving will continue moving at the same speed. The amount of friction between 2 surfaces depends on what 2 factors? 1) the kinds of surfaces 2)the force pressing the surfaces together. What are microwelds? They are kinds of surfaces What is the frictional force that prevents two surfaces from sliding past each other? Sliding Friction What is the frictional force that opposes ttwo surface from sliding past each other? Sliding Friction What is the frictional force between a rolling object and the surface it rolls on ? rolling friction What is the friction-like force that opposes the motion of objects that move through the air (depends on the speed, size, & shape of the object) air resistance What is the highest speed a falling object will reach before air resistance= the acceleration due to gravity? called terminal velocity is 9.8 m/s what is an attractive force between any 2 objects that depends on the masses of the objects and the distance between them? Gravity What are the 4 basic forces of gravity? 1) Gravity 2) Electromagnetic force 3) strong nuclear force 4) weak nuclear force what calculates the force of gravity between 2 objects if their masses and distance between them is known the law of universal gravitation What is the formula for force? F=G m1m2/d2 what is the acceleration of falling objects on Earth due to the force of gravity? 9.8m/sec2 What is the property called that is related to how much force is needed to change the motion of an object? Momentum What is the formula for momentum? momentum (p)= mass (m) * velocity (v) p=mv This is not a question - it is an assignment - please do the practice problems on p.86 this answer can only be right after you have done these Momentum is not created nor destroyed - it just changes forms (or gets transferred from one object to another) - What is this law called? The Law of Conservation of Momentum the formula to find the force of Earth's gravity will always be.... Force of gravity (N) = mass (kg)*acceleration Acceleration due to gravity is always how much? 9.8 m/s2 What would the gravitational force be on a sky diver with a mass of 60kg use your formula to solve! How do you calculate weight of something or someone on earth? (formula) Weight = mass x 9.8m/sec2 What do we call the gravitational force on a mass? it's weight Why do astronauts appear to be weightless in space? a space shuttle is in free fall but it is falling around the Earth rather than straight downward (see fig 15 pg 79) How are horizontal & vertical motions affected by gravity? check out you textbook - p. 80, fig 16 & 17 The net force exerted toward the center of a curved path is called centripetal force What force keeps your car's traction moving around a curved path? Centripetal Force acceleration toward the center of a curved path is _____ centripetal acceleration State Newton's 3rd Law of Motioin For every action force, there is an equal and opposite reaction Give 2 examples of Newton's 3rd law in action 1) rocket propulsion 2) skaters pushing against a wall and moving backward (p. 83, fig 21) What is a property that is related to how much force is needed to change the motion of an object? Momentum What Law says that momentum is not created nor destroyed it just changes forms ( or gets transferred from one object to another) ? Law of Conservation of Momentum What is the law for Momentum? p(momentum)=m(k/g) times v(m/s)

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