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# Newton's Second Law of Motion: Acceleration of the Coffee Mug (page 2)

By John Wiley & Sons, Inc.
Updated on Dec 13, 2010

Newton's second law of motion says that the acceleration of an object is directly proportional to the net force on, and inversely proportional to the mass of, the object. Acceleration is the change in velocity over time. Newton's law can be stated with this equation: Force (F) = mass (m) × acceleration (a). As the force acting on an object increases, the acceleration increases. As the mass of the object increases, the acceleration of the object decreases. In this activity you will observe the effect of Newton's second law of motion on a coffee mug.

### Materials

Large ceramic coffee mug with a handle

Spring scale

Small container of sand

### Activity

1. Place the coffee mug at the end of a table farthest away from you. Hook the spring scale on the handle of the mug.
2. Pull the mug across the table at a very slow but constant speed. Look at the spring scale and read the force you are exerting. Record that force.
3. Repeat step 2, but this time increase the acceleration of the pull as you pull the coffee mug. Observe the spring scale reading.
4. Fill the coffee mug with sand and repeat steps 2 and 3. Note and record the readings on the spring scale each time.

### Follow-Up Questions

1. Look over your results. Did you see a correlation between force and acceleration? If so, what was it?
2. Did you see a correlation between acceleration and mass? If so, what was it?

1. Yes, they are directly proportional.
2. Yes, they are inversely proportional.

### Extension

Calculate the acceleration in all three cases by using the formula F = ma. You can rearrange the formula as a = F/m. You will need to find the mass of the coffee mug without the sand and with the sand to carry out these calculations.