Student Exploration: Atwood Machine (gizmos)

How could Jane get to the branch at the same time that Tarzan travels to the ground?

He could tie the vine to the branch and then Jane could climb the vine while Tarzan gets off.

Which mass do you think will move down?

Mass B

Which mass do you think will move up?

Mass A

Click Play (). What happens?

Mass B goes down until it hits the surface and while Mass B was going down, Mass A was going up.

What is the force that pulls mass B downward?

Force of gravity

Predict: How do you think the speed at which the heavier object descends depends on the difference between the two masses?

The greater the difference between the masses of the object, the faster the heavier object would descend.

Analyze: How does the difference in masses affect the speed at which mass B descends?

The greater the mass the less time it takes for the object to descend.

Think and discuss: What do you notice about the effect of adding more and more mass? (In other words, does each 1-kg addition of mass have the same effect?)

Adding more mass does not have a constant effect on the time. The more the mass increases the smaller the difference between the time gets.

Predict: Next, you will investigate different mass combinations in which the mass difference is always the same. If the difference in mass is 1 kg, how do you think the total mass will affect how quickly the two objects move?

I think the time will be the same because the difference in mass will be the same.

Analyze: Given the same mass difference, how does the total mass affect how quickly the weights move?

The higher the total mass of the objects are, the longer it takes for the object to descend.

Think and discuss: Given the same mass difference, why do you think the masses move most quickly when the total mass is smallest?

because then it will require less force of gravity which would move the object quicker

Calculate: The weight of an object is equal to the product of its mass and gravitational acceleration, which is 9.81 m/s2 on Earth's surface. Weight is measured in newtons. What is the weight of each object?

Object A: 9.81 N
Object B: 19.62 N

How does the gravitational force on each object compare to its weight?

The gravitational pull for an object with more mass would be higher.

For which object is the tension greater than the weight?

Object A which has a smaller mass.

For which object is the tension less than the weight?

Object B

Click Play. What happens?

Object B descends to the ground, while object A rises upwards.

What is the final velocity of mass A?

2.55 m/s

How long did it take for object A to reach the top?

0.78 s

What is the acceleration of mass A?

3.27 m/s/s

Calculate: The Atwood machine was designed to demonstrate Newton's second law, which states that force (F) is equal to the product of mass (m) and acceleration (a): F = ma. Because they are connected, you can treat both masses as part of the same system. Select the DESCRIPTION tab. What is the total mass of masses A and B?

3.0 kg

What is the difference between the gravitational force on B and on A?

9.81 N

Based on Newton's second law, what is the acceleration of each mass?

3.27 m/s/s