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Fundamental Quantities and Units

Fundamental Quantity MKS Unit

* Length (Meters)

* Mass (Kilograms)

* Time (Seconds)

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Motion

Quantity Symbol Definition Units

Distance d m

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Motion

The symbol “Δ” means “Change in”

Quantity Symbol Definition Units

Distance d m

Speed v d/Δt m/s

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Motion

The symbol “Δ” means “Change in”

Quantity Symbol Definition Units

Distance d m

Speed v d/Δt m/s

Acceleration a Δv/Δt m/s2

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Part 2, B: MOTION

Derived Quantity - Acceleration

An object is moving with a speed of 3 m/secand accelerates at 4 m/sec . What is itsspeed after 1 sec, 2 sec, etc?

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Part 2, B: MOTION

Derived Quantity - Acceleration

An object is moving with a speed of 3 m/secand accelerates at 4 m/sec . What is itsspeed after 1 sec, 2 sec, etc?

The speed changes by 4 m/sec every second

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Part 2, B: MOTION

Derived Quantity - Acceleration

An object is moving with a speed of 3 m/secand accelerates at 4 m/sec . What is itsspeed after 1 sec, 2 sec, etc?

After 1 sec v = 7 m/sec

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Part 2, B: MOTION

Derived Quantity - Acceleration

An object is moving with a speed of 3 m/secand accelerates at 4 m/sec . What is itsspeed after 1 sec, 2 sec, etc?

After 1 sec v = 7 m/sec

After 2 sec v = 11 m/sec

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Part 2, B: MOTION

Derived Quantity - Acceleration

An object is moving with a speed of 3 m/secand accelerates at 4 m/sec . What is itsspeed after 1 sec, 2 sec, etc?

After 1 sec v = 7 m/sec

After 2 sec v = 11 m/sec

After 3 sec v = 15 m/sec

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Motion

Relationships

If a = 0

d = vt

If a ≠ 0

d = ½ a t2

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Part 2, B: MOTION

Derived Quantity - Acceleration

Observation (Galileo): All objects in freefall near the surface of the earth accelerateat 9.8 m/sec toward the surface of theearth.

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Part 2, B: MOTION

Derived Quantity - Acceleration

Observation (Galileo): All objects in freefall near the surface of the earth accelerateat 9.8 m/sec toward the surface of theearth.

Free Fall: Any motion for which the onlyinfluence is gravity.

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Motion

An object is thrown vertically upward from the surface of the earth in the absence of air resistance.

Note: this can be accomplished, for example, in an experimental facility from which the atmosphere has been removed.

1. What is the acceleration of the object on its way up?

2. What is the acceleration of the object on its way down?

3. If the object is thrown vertically, it will stop at the highest point in its motion. What is the acceleration of the object at the moment that it stops?

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Motion

Air Hockey

There is no friction between the puck and the table surface

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Motion

Free Fall Tower

Drop distance - dd

y Height above base - y

100 m

Assumption: No air resistance

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Motion

1. Assume the air hockey puck moves with an initial speed of 10 m/s. What is its position (assume it starts a 0 m) after 1 s, 2 s, 3 s, 4 s and 5 s?

2. Assume the Free Fall Tower is 100 m high. What is the drop distance and the height above the base after 1 s, 2 s, 3 s, 4 s and 5 s? Assume g = 10 m/s2 .

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Motion

Can be a combination

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Motion

Can be a combination

d = ½ a t2

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Motion

Can be a combination

d = ½ a t2

d = v t