# Machines video lecture

Created 3 years ago

Duration 0:30:19
261
Slide Content

• Efficiency
2. ### Slide 2 - Simple Machines

• Lever
• Inclined Plane
• Pulley
• Wheel & axle
• Wedge
• Screw
3. ### Slide 3 - Lever

• F in
• F out
• din =distance between applied force and fulcrum
• dout =distance between load and fulcrum
• hin = the heigt force end moves
• hout = the height load end moves
• hin
• hout
• dout
• din
• dout
• din
• See-saw
• Scissors
• pliers
• Hole puncher
• Bottle opener
• wheelbarrow
• Fishing rod
• tweezers
• tongs
4. ### Slide 4

• Inclined Plane:
• Output Force = Fout
• Input Force = Fin
• Work input = Work Output
• W in = W out
• F in  d in = F out  d out
• Input distance= din
• Output distance = dout
5. ### Slide 5 - What if there is friction?:

• Work input + Work done by friction = Work Output
• W in + W f = W out
6. ### Slide 6 - Mechanical Advantage

• Ideal Mechanical Advantage (IMA) depends only on the geometry of the system.
• However situations are never ideal!
7. ### Slide 7 - Efficiency:

• The ratio of the work output to work input.
8. ### Slide 8 - Ex:

• Clyde, a stubborn 350 kg mule refuses to walk into the barn, so farmer McDonald must drag him up a 5 m ramp, which stands 0.5 m above ground level. He pulls with 450 N of force.
• What is the ideal MA?
• Find work input, work output and friction.
• What is the actual MA?
• Find the Efficiency of the ramp.
9. ### Slide 9 - Ex:

• Clyde, a stubborn 350 kg mule refuses to walk into the barn, so farmer McDonald must drag him up a 5 m ramp, which stands 0.5 m above ground level. He pulls with 450 N of force.
• What is the ideal MA?
• Find work input, work output and friction.
• What is the actual MA?
• Find the Efficiency of the ramp.
10. ### Slide 10 - Ex:

• Winnie holds a 50 N tray of lemonades in one hand. The length of her arm from her hand to elbow is 30 cm and her biceps exert a force 5 cm from her elbow. How much force must her biceps exert to allow her to hold the tray?
11. ### Slide 11 - Ex:

• Winnie holds a 50 N tray of lemonades in one hand. The length of her arm from her hand to elbow is 30 cm and her biceps exert a force 5 cm from her elbow. How much force must her biceps exert to allow her to hold the tray?

13. ### Slide 13 - Ex:

• Using a pulley system, Sam lifts the 1000 N engine 0.5 m, but exerts a force of 60 N on 10 m of rope to do so.
• What is the theoretical (ideal) mechanical advantage of the pulley system? How many supporting strands does it have?
• What is the ACTUAL mechanical advantage of the pulley system?
• How much work is done on the engine? How much work does Sam do?
• What is the work done by friction?
14. ### Slide 14 - Ex:

• Using a pulley system, Sam lifts the 1000 N engine 0.5 m, but exerts a force of 60 N on 10 m of rope to do so.
• What is the theoretical (ideal) mechanical advantage of the pulley system? How many supporting strands does it have?
• What is the ACTUAL mechanical advantage of the pulley system?
• How much work is done on the engine? How much work does Sam do?
• What is the work done by friction?