Reference Points
What is a reference point?
A place or object used to determine if something is in motion. (It does not move)
What is a balanced force?
Equal forces acting on an object in opposite directions that cause no change in motion.
Which of Newton’s Laws explains inertia?
Newton’s 1st Law.
What is the formula for speed?
Speed = Distance ÷ Time
Pablo’s horse weighs 1000 lbs. What does this measure?
Weight.
From which reference point does a puppy in a wagon being pulled on a sidewalk appear to be moving?
The sidewalk.
What is an unbalanced force?
Forces that are not equal, causing a change in the object’s motion
According to Newton’s 3rd Law, how does the tablecloth trick work?
The action of pulling the cloth creates an equal and opposite reaction, while the dishes stay still due to inertia.
If Nicki rides 15 km in 3 hours, what is her average speed?
5 km/h
What is another term ( word ) for weight
Mass
Why does the sidewalk make a good reference point in motion problems?
Because it stays still and doesn’t move with the object.
In tug-of-war, if one side pulls with 50 N and the other with 35 N, what is the net force?
15 N to the left.
Why did the food bowl move across the room each morning?
According to Newton’s 1st Law, the dog applied force to the bowl, causing it to move.
Why is Janie’s velocity report inaccurate?
Why is Janie’s velocity report inaccurate?
Nick ran 200 meters in 50 seconds during a race. Then he ran another 300 meters in 75 seconds. What was his average speed for the entire race?
Total distance = 200 m + 300 m = 500 m
Total time = 50 s + 75 s = 125 s
Average speed = 500 ÷ 125 = 4 m/s
True or False: An object is moving if its distance from a reference point is changing.
True.
Which type of friction slows down a falling feather?
Fluid friction (air resistance).
What happens to acceleration if mass increases but force stays the same?
Acceleration decreases.
What two measurements do you need to calculate acceleration?
Change in speed and time.
A dog pulls left with 32 N, a small dog pulls right with 24 N. What is the net force?
8 N to the left.
Create your own example of motion and identify the reference point.
Answers will vary (e.g., “A car moving past a mailbox – the mailbox is the reference point.”)
Explain why fluid friction affects a feather more than a ball.
A feather has more surface area and less mass, so air resistance slows it down more than the heavier, denser ball.
Explain how all three of Newton’s Laws apply to the tablecloth and dishes trick.
1st Law: The dishes stayed in place due to inertia.
2nd Law: Force caused the tablecloth to move.
3rd Law: The pull on the tablecloth created a reaction force.
A balloon falls faster with each second. Is it moving at constant speed or accelerating?
Accelerating.
In a graph showing the distance a balloon travels every 0.25 seconds, how can you tell if it is accelerating?
In a graph showing the distance a balloon travels every 0.25 seconds, how can you tell if it is accelerating?