1. Lab Assessment: A force probe was used to apply a force of different magnitudes to 3 different carts on a frictionless track. The resulting ΣF and acceleration data was graphed. What is the difference between each cart? Label each line appropriately.

2. What does a scale measure?

3. force exerted by the scale.
A scale measures the
force exerted by the scale.
This does not necessarily equal
the force the earth exerts on an object

4. Hang your mass from the spring scale
Hang your mass from the spring scale. Draw a force diagram for your mass. Then determine the force exerted by the Earth on the mass.

6. FEarth on Object (N)
7.0
6.0
5.0
4.0
3.0
2.0
1.0
Mass (kg)
Slope = 9.8 N/kg

7. Mass (kg)
The ratio of gravitational force to mass is constant for all objects – the gravitational constant g, already familiar to us as free-fall acceleration.
Slope = 9.8 N/kg
FEarth on Object (N)

8. Gravitational Force
The gravitational force that Earth exerts on an object when on or near its surface:
Where g = 9.8 m/s2 = 9.8 N/kg on or near Earth’s surface. The force points toward the center of Earth.

9. The gravitational force that Earth exerts on an object is proportional to the object’s mass.
The Earth exerts a stronger gravitational force on an object with more mass.

10. Mass is the quantity of matter that composes an object.
Weight is the gravitational force that a planet exerts on an object.
gEarth = 9.8 N/kg
gMoon = 1.6 N/kg

11. Watch Your Language!
We will not use the term “weight of an object” because it implies that weight is a property of the object, rather than an interaction between two objects.

12. WB A 1-kg soccer ball and a 10-kg bowling ball are released from rest in the absence of air resistance.
a)Draw a force diagram for each object after release.
b)Use the gravitational force law and Newton’s 2nd Law to solve for the acceleration of each.
c)Analyze your results, and use physics concepts (not just math) to explain why you obtained these values.

14. Why Do All Objects Fall at the Same Rate?
Because the same property that causes them to feel a gravitational force also causes them to resist acceleration.