Forces + Motion
What happens to motion when forces are balanced? What happens to motion when forces are unbalanced?
Balanced: motion stays the same
Unbalanced: motion changes
A puck on ice begins to slow down after some time. Why?
Friction makes the puck slow down.
How do you make magnets attract? How do you make magnets repel?
Attract: Opposite poles
Repel: Same poles
How many variables can we change when we're doing an experiment?
One variable
What direction does friction always go to?
To the opposite direction of movement
Describe the forces when a sky diver falls at a constant speed
The forces are balanced.
What are the forces acting on a pencil that stays still?
1. Normal Force (pushing up) 2. Gravity (pulling down)
Choose the correct items that can be attracted to a magnet: iron, wood, steel, silver, rubber, gold
Iron, steel
Before building the prototype, what two things do scientists have to do?
1. Research
2. Come up with a plan
Two dogs are pulling on a toy, but the toy stays in the same place. How would you describe the forces?
The forces are balanced.
In space, a satellite can travel for hundreds of years without needing to recharge or get more fuel. Why can they go forever? Be specific
In space, there is no friction to slow things down
A car drives across a road at a steady speed. What are the two main forces affecting the speed?
1. Gravity (pulls down) 2. Friction (pushes back)
A student puts the south pole of one magnet facing the north pole of another magnet, but they are not attracting. How can we fix this?
Put the magnets closer
One day in class, we wanted to know how elastic force works. So, we came up with a question: How does the number of twists affect the speed of the car? What was the variable that we changed in that question?
The number of twists
Two students are playing baseball. Player A hits a ball that travelled 60 mph, but Player B hit a ball that travelled 85 mph. Who hit the ball with more force? Explain.
Player B because their ball travelled faster. We know stronger forces can make a motion go faster.
A car starts still while being held on both sides. On the left side, there is a hand; on the right side, there is a rope attached to heavy weight. How will the motion change when we let go of the car and why? Be specific
The car will begin to move to the right side because the forces are unbalanced.
Belinda and Zion are pushing against a box with 150 N of force, but the box does not move. Explain why.
Their force is not stronger than friction
A company wants to design a suitcase that uses magnets instead of zippers, since they tend to get stuck more easily.
Draw a model to show how it will work.
The buttons of the magnet have to be attracting to each other with opposite poles.
You want to test how the strength of a push affects how far a ball rolls. How would you set up the experiment? What variable are you changing? What are you measuring? What needs to stay the same?
Change: The strength
Same: Table, Ball, Etc
Measure: Distance/Length
An engineer has two diagrams: a train powered by magnets, and another train that uses wheels. If the goal is to have the train travel as fast as possible, which design should they choose? Explain why.
The Meglev train travels faster because it has less friction since it's being repelled against the floor
Draw a model with forces to explain how a person can slide down a hill and get faster and faster.
1. Hill
2. Small friction arrow going the opposite way
3. Larger gravity arrow going with motion
4. Normal Force optional
A soccer ball is sitting still. Then someone kicks it and it rolls across the field (not in the air). The ball slows down over time. What different forces are acting on the ball from start to finish?
1. Normal Force + Gravity
2. Kick Force + Gravity + NF + Friciton
3. Gravity + NF + Friction
You're designing a game where players have to move the pieces through a maze without actually touching the objects. What are two things you would need to think about before building the prototype?
1. The board and pieces have to be magnetic
2. They have to be close to each other,
A toy car is rolling down a ramp. You want to design an experiment to test how the height of the ramp affects the car's speed. What would you change, what would you measure, and what would you keep the same?
Change: Height of the car
Same: Car, Table, Etc
Measure: Car's Speed
A student dropped two pieces of paper that weigh the same, but one of them fell faster than the other. Why did one piece of paper fall faster?
The piece of paper that fell faster must have less friction from the air. That piece of paper must have been crumpled.