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Skating 1
Skating
Skating 2
Question:
A rotary lawn mower spins its sharp blade
rapidly over the lawn and cuts the tops
of the grasses off. Would the blade still
cut the grasses if they weren’t attached
to the ground?
Skating 3
Observations
About Skating
• When you’re at rest on a level surface:
– If not pushed, you stay stationary
– If pushed, you start moving in that direction
• When you’re moving on a level surface:
– If not pushed, you coast steadily and straight
– If pushed, you change direction or speed
Skating 4
Physics Concept
• Inertia
– A body at rest tends to remain at rest
– A body in motion tends to remain in motion
Skating 5
Newton’s First Law,
First Version
An object that is free of external influences
moves in a straight line and covers equal
distances in equal times.
Skating 6
Physical Quantities
• Position – an object’s location
• Velocity – its change in position with time
