7.2. Power Requirements of Machines

Try these first

1. 1.

   Define rolling resistance.

   Hint

   Think about the friction created when a wheel rolls.

2. 2.

   What is grade resistance?

   Hint

   Consider slopes when a vehicle moves uphill.

3. 3.

   What two types of resistance must be overcome for effective machine operation?

   • Wind resistance and water resistance
   • Rolling resistance and grade resistance
   • Friction resistance and inertia resistance

   Hint

   Consider the surfaces and slopes that machines operate on.

4. 4.

   True or False: Rolling resistance decreases as the speed of the machine increases.

   • True
   • False

   Hint

   Think about what rolling resistance actually measures.

5. 5.

   A 25-ton excavator with a rolling resistance of 50 kg per ton is moving on a gravel road. It encounters a grade resistance of 450 kg due to a 10-degree slope. Calculate the total tractive effort required.

   Hint

   Don’t forget to account for both rolling and grade resistance!

6. 6.

   Discuss how different industrial scenarios might influence the selection of machinery based on power requirements. Use examples from construction, mining, and agricultural operations.

   Hint

   Consider how job sites differ in terms of terrain and material.