Motion
When you know both the speed and direction of an objects motion, you know its _____________.
Velocity
What is the equation for velocity?
v = d / t
True or False: When all of the forces on an object are balanced, the object is accelerating.
False
Newton's first law states that an object at rest/in motion will stay at rest/in motion unless acted on by a(n) ___________________.
Unbalanced Force
According to Newton's third law, what is the strength of a reaction force? What direction does it act in?
Equal strength to the action force.
Opposite direction of the action force.
What do you need to do to an object in order to change it's motion?
You need to apply an unbalanced force
What are the 3 ways that an object can accelerate?
1) Speed Up
2) Slow Down
3) Change Direction
What direction does friction ALWAYS act in?
The opposite of an object's motion.
According to Newton's second law, if you divide the force acting on an object in half, what happens to its acceleration?
It also divides in half.
Newton's first law states that an object in motion stays in motion.
When we push a book across the desk, why does it stop?
Because the law ends with "unless acted on by an unbalanced force."
Sliding friction is an unbalanced force that causes the book to change it's motion.
What is a reference point?
A place/object used for comparison to determine whether an object is in motion.
What units do we usually use for acceleration?
Meters per Second per Second (m/s2)
You and a friend are pushing a couch across the room. If you push with a 55 Newton force and your friend pushed with a 70 Newton force (in the same direction), what is the Net Force on the couch?
125 Newtons
Why don't action/reaction forces cancel each other out (balance)?
Because they are acting on different objects
A block and a toy car with equal mass are sitting on a ramp. The car moves down the ramp but the block does not. Why?
Gravity is pulling both objects down. Since rolling friction is weaker than sliding/static friction, the car is not being pushed up as strongly as the block, so the Net Force causes the car to roll down.
What does the slope of a distance vs. time graph tell you? What does a curved line represent?
a) The speed of an object.
b) The speed is changing (acceleration)
How much time does it take a dolphin to swim 20 km if it is swimming with a velocity of 50 km/hr?
0.4 hours
What is the strength of a force that accelerates a 500 kg hippo at a rate of 5 m/s2 to the right?
2500 Newtons to the right
What is inertia? If you increase the mass of an object, what happens to its inertia?
Inertia is a resistance to a change in motion.
Since inertia depends on mass, when you increase the mass of an object you also increase its inertia (making it harder to move).
Why does a slip-n-slide work better with water on it than without water on it?
Adding water changes the friction from sliding to fluid, which is weaker, so the surface pushes less against you and you continue to move more easily.
Look at the picture in this link: https://drive.google.com/file/d/1zQTbd2ixLyNcUGt6_tpBj8IRir6H2eci/view?usp=sharing
How fast is the person in the picture moving using the following as a reference point:
a) The Bus
b) The Ground
c) Someone in outer space
a) 3 km/ hr
b) 53 km/ hr
c) 2253 km/hr
What is the difference between speed and velocity. If you are driving to Disneyland, which of these is more important for the driver to understand?
Velocity includes direction, speed does not.
You would want the driver to understand velocity, so that they drive both fast AND in the right direction.
You are pushing a shopping cart with your best friend in it and suddenly stop the cart. What happens to your friend? Why?
Your friend continues moving forward due to inertia, an object's resistance to a change in motion. (Newton's First Law) Since there was no unbalanced force acting on your friend (in motion), he/she keeps moving until there is an unbalanced force.
Identify the Action/Reaction force pair that causes you to move up when you jump. What law is this based on?
Action is you pushing down on the ground.
Reaction is the ground pushing up on you.
This is based on Newton's 3rd law.
You slide a book across the table to your friend. Draw a picture of this situation and label each force acting on the book as it slides. Include an arrow representing the direction that each force is acting in.
(See Picture)