uNiT 2 MoTiOn AnD fOrCe

Speed

(s) the distance an object travels per unit of time.

Velocity

(v) the speed of an object and the direction of its motion.

Displacement

(Δx - change of x) distance and direction of an object's change in position; difference from starting to ending point.

Newton's 2nd Law

-A net force acting on an object causes the object to accelerate in the direction of the net force. -The greater the mass, the greater the force needed to accelerate it. -The greater the net force, the greater the acceleration. Exp-If you use the same force to push a truck and push a car, the car will have more acceleration than the truck, because the car has less mass

Newton's 1st Law

-An object will move at a constant velocity until a net force acts on it. -An object in motion will stay in motion unless a force acts on it. -An object at rest will stay at rest unless a force acts on it. Exp- A cup wont move if you don't touch it

Newton's 3rd Law

-Every action has an equal and opposite reaction. -When one object exerts a force on a second object, the second one exerts a force on the first that is equal in size and opposite in direction. Ex. When you jump on a trampoline, the trampoline exerts the same force on you but pushes you the opposite direction.

terminal velocity

-Maximum velocity a falling object will reach -Occurs when the force of gravity and air resistance become balanced -Net force = 0 therefore no acceleration -Force of gravity pulls you down. Force of air resistance opposes the opposite direction. 55 m/s or 118.06 mi/hr in Humans

objects ranked from LEAST inertia to MOST

1. feather 2. baseball 3. small car 4. truck 5. large train

A baseball player hits a ball towards the outfield.

2nd law

A motorcycle can reach a speed of 60 mi hr much faster than a minivan

2nd law

Swimming in a pool requires that you push back on the water in order to go forward.

3rd law

reference point

An indicator that orients you; the place from where you measure, record, or witness an event

law of universal gravitation

Any two masses exert an attractive force on each other. Depends on: --Mass: the greater the mass, the greater the gravitational attraction --Distance: the closer the distance, the greater the gravitational attraction

Explain the difference between balanced and unbalanced forces.

Balanced Forces: forces that are equal in size and opposite in direction. -Does not cause a change in motion because the net force on the object is 0. Unbalanced Forces: forces that are not equal in size and opposite in direction. -Net force causes the object to move in the direction of the force.

Air Resistance (drag)

Determined by: 1. Speed -The greater the speed the greater the resistance 2. Size -The larger the object the greater the resistance 3. Shape -The flatter the object the greater the resistance

Newton's 2nd Law of Motion conversion

F = Force Measured in N m = mass Measured in kg a = acceleration Measured in m/s2

Find the weight of a suitcase that has a mass of 42 kg.

F= 411.6N

Force causes all falling objects to have an acceleration due to gravity of 9.8 m/s2.

Gravity

Newton's 1st Law is also known as the Law of Inertia.

Inertia: The tendency of an object to resist a change in motion. -The more mass an object has, the more inertia it has.

Law of Conservation of Momentum

Momentum is never created or destroyed in a collision, it only is transferred. (p) mass in motion. p = mv p = momentum Measured in kg*m/s m = mass Measured in kg v = velocity Measured in m/s

list the different ways an object can accelerate

Positive acceleration, negative acceleration, or changing direction

Differentiate between the factor(s) that affect inertia and momentum.

So, inertia describes an object's resistance to change in motion (or lack of motion), and momentum describes how much motion it has.

Explain the difference between the 3 types of friction

Static Friction: force between two surfaces that are NOT moving past each other Sliding Friction: force between two surfaces that are sliding past each other Rolling Friction: force between a rolling object and the surface it rolls on.

Gravity: the attraction two objects have on one another The force of gravity pulls us towards Earth.

The attraction two objects have on one another -The force of gravity pulls us towards Earth.

Weight

The force of gravity on an object -Because it is a force, you can always calculate weight using F = ma -When finding weight, acceleration due to gravity is always used = 9.8 m/s squared

Explain what the slopes on a distance vs time graph and on a velocity vs time graph tell you.

The slope on a distance vs time graph show you the speed of an object, and the slope on a velocity vs time graph show you the acceleration of an object.

Inertia

The tendency of an object to resist a change in motion.

Motion

When an object changes its position.

You are pushing a friend on a sled. You push with a force of 40N. Your friend and the sled together have a mass of 80 kg. Ignoring friction, what is the acceleration of your friend on the sled?

a = 0.5 m/s2

velocity vs time graph- object slowing down

change the distance to velocity

How much does a 200 kg car weigh?

f=ma f=?N m=200kg a=9.8m/s2 f= 200kg x 9.8m/s2= 1960N

3 common forces that can be applied to objects

friction, air resistance, and gravity

distance

how far an object has moved

WHat is the mass of an object that is experiencing a net force of 200 N and an acceleration of 500 m/s2?

m=f/a m=?kg f=200N a= 500 m/s2 m=200N/500 m/s2= 0.4kg

2 factors for gravitational pull

mass and distance

Force

push or pull one object exerts on another. -Measured in Newtons ( 1 N = 1 kg*m/s2) -Forces can cause a change in an object's motion. -More than one force can act on an object at one time.

Acceleration

rate of change of velocity over time.An object is considered to be accelerating when it speeds up, slows down, or changes direction. Measured in mi/hr2, m/s2, km/hr2, etc.

air resistance

resistance an object feels when travelling through the air.

Friction

resistance to motion when two objects are in contact with one another.

net force

the combining of forces when two or more forces act on an object.

instantaneous speed

the speed at any given point - what shows up on your speedometer.

Average Speed

total distance traveled divided by total time traveled.

An 8-kilogram bowling ball is rolling in a straight line toward you. If its momentum is 16 kg x m/s, how fast is it traveling?

v=p/m v=?m/s P=16 kg x m/s m=8kg v= 16kg x m/s / 8kg= 2 m/s