Exercise 2.1: External Forces

1. What is mass? What units do we use to measure it?

2. What is weight? What units do we use to measure it?

3. If an object has a mass of 18 kg, what is its weight? Show all the steps in your calculation.

This image shows two men moving a heavy refrigerator up a set of stairs. They are wearing a shoulder strap that goes underneath the fridge. This allows them to carry the weight of it on their shoulders rather than trying to hold the fridge with their hands and arms.

4. What forces are acting on the fridge? Name at least 4.

5. Which directions are each of these forces acting in?

6. Which of these forces has the greatest magnitude? Which has the least? Remember that the fridge is moving up the stairs.

7. Where is friction acting in this picture? Would increasing the force of friction make it easier or more difficult to move the fridge? Why?

8. The shoulder strap that the men are using is supporting the weight of the fridge from underneath. If the strap was wrapped around the middle of the fridge instead, would that improve the ability to move the load? Why or why not?

9. Why is carrying a load on your shoulders more efficient than carrying a load on your arms?