**Evans SPH 4U1**

**Physics Grade 12**

**Unit 3: Circular Motion**

**Note 2: Apparent Weight**

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Reference Chapter 3.2 & Section page 148

**Non-inertial Frame of Reference:
**An accelerating frame of reference where the Law of Inertia (Newton's 1st
Law) does not hold.

**Apparent Weight:** The net force
on an accelerating object in its non-inertial frame of reference (i.e. If you
are in an elevator accelerating downward the normal force pushing up on you is
less so your apparent weight is less).

**Centrifuge:** rapidly-rotating
object used to separate substances according to their densities.

~ Throw a ball, throw it further, fire a cannon, keep extending the reach and what will the trajectory be?

~ Where is the space shuttle in
relation to earth? Why do astronauts feel weightless?

(often referred to with misleading terms such as free fall, zero gravity,
microgravity). Note: The absence of forces against astronauts' muscles cause the
muscles to become smaller and bones to become brittle.

**Centrifugal Force:** Do you
weigh more at the equator or at the poles? ~ demo on globe

**Coriolis Force: ~**demo pendulum
at north pole on globe

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** Example 1:**

A 58 kg test pilot flies her plane in a vertical circular loop of radius 640m at a constant speed of 140 m/s. Determine the force the seat exerts on her::

a) At the bottom of the loop**
Answer: 2.3 x 10 ^{3} N [Up]**

b) At the top of the loop **
Answer: 1.2 x 10 ^{3} N [down]**

c) Calculate the minimum speed that
will result in the pilot feeling "weightless" at the top of the loop.
**Answer: 7.9 x 10 ^{1 } m/s**

**Example 2:**

A pilot having a mass of 8.0 x 10 kg,
executes a vertical loop of radius 6.0 x 10^{ 2} m in his plane.
What force does the pilot exert on his seat at the bottom of the vertical loop
if his speed is 1.8x 10^{ 2 }m/s? **Answer: The seat exerts a force
of 5.1 x 10 ^{3 }N [up] on the pilot so therefore the pilot exerts a
force of 5.1 x 10^{ 3} N [down] on the seat.**

**Example 3:**

If the earth's radius is approx. 6100 km find the orbital velocity that the shuttle would have.

**Answer: 27 835 km/h **