Forces
What is a force?
What is a variable?
Something in the design of the investigation that we change.
What is a control?
Something in the design of the investigation that stays the same
How many variables can their be in an investigation?
1
What is gravity?
The force that pulls us down to Earth
When do magnets attract & when do they repel?
Attract - opposite sides
Repel - Same sides
Some students are designing an experiment to test the effect of force on an object. The force they are testing is friction. The students will investigate how far a car will slide when rolled across surfaces with different textures.
What is should the variable in this scenario?
1. the ramp height
2. the ramp length
3. the texture of the ramp
4. the distance the car travels
3. the texture of the ramp
Some students were investigating which surfaces would allow a ball to roll the farthest. Which of the following would be essential in their investigation?
1. stopwatch
2. meter stick
3. calculator
2. meter stick
How many controls can their be in an investigation?
No limit
The force of gravity pulls the box down so it takes less effort to drop it. If you pick it up, you are working against the force of gravity.
If two students are pushing a box and the student on the right pushes the box with more force than the student on the left which way will it move?
to the left
Is the following question a testable question in the classroom? Explain your answer.
What type of surface produces the most friction.
Yes, this is a testable question, because we have different surfaces available in the classroom. We also have done a friction lab and we tested the force of friction on a water bottle with carpet and the desks.
Is the following question a testable question in the classroom? Explain your answer.
How does gravity affect the movement of comets?
No, this is not a testable question because we don't have access to comets in the classroom.
Is the following question a testable question in the classroom? Explain your answer.
What evidence supports the theory of black holes?
No, this is not a testable question for two reasons: 1. we do not have access to black holes in the classroom, 2. we could easily google the existing evidence that supports this theory.
If a surface has less friction will a ball roll on it faster or slower?
If a surface has less friction will a ball roll farther or will it stop sooner?
It will roll faster and farther.
If a surface has more friction will a ball roll on it faster or slower?
If a surface has more friction will a ball roll farther or will it stop sooner?
It will roll slower and it will stop sooner.
To make sure your results are valid.
Why can you only have one variable in an investigation?
If you change too many things, you want know what caused the change in your results.
Why are controls necessary?
We need control in an investigation in order to ensure that we are only testing one thing and we have accurate results.
Doing work is exerting a force and causing an object to change its motion and position.
Give 3 examples of doing work.
Answers may vary, but must include something about you pushing or pulling an object in order to change the motion and position of it.
Some students wanted to find out if a tennis ball and a baseball dropped from the same height hit the ground at the same time. This investigation tests the effect of which of the following?
Gravity
A student designed an experiment to determine which type of ball would roll the farthest. The student used 3 types of balls on 3 different surfaces, each with a different mass.
What should the student do to improve their experiment?
Use the same surface for each trial.
If a student pulls a 2 kg box of marbles with a spring scale and then a 4kg box of marbles with a spring scale across the same surface, what are they testing?
hint: How _______ affects _________.
How mass affects the force needed to move objects.
A student uses a spring scale to pull a 50-gram block horizontally across a wood desk. Then, the student pulls the block the same distance across surfaces of carpet, sandpaper, and glass.
Which question is this investigation designed to answer?
Hint: How ______ affects ______
How different surfaces/ friction levels affect the amount of force need to move a block.