#### Transcript g (N/kg) - Quantum Tunneling

```3.1-3.2
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The gravitational field strength is the amount
of force acting on each kilogram of mass.
It is measured in N/Kg.
It is not the same everywhere.
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The gravitational field strength is a vector
quantity whose direction is always toward the
center of the earth.
As the gravitational field strength and the
acceleration due to gravity are numerically
equal, the same symbol, g, is used for both.
g = 9.8 N/kg, or g = 9.8 m/s2
9.8 N/kg is an average for the earth’s surface
Latitude (⁰)
g (N/kg)
Distance to centre
(km)
0 (equator)
9.7805
6378
15
9.7839
6377
30
9.7934
6373
45
9.8063
6367
60
9.8192
6362
75
9.8287
6358
90 (north pole)
9.8322
6357
The force of
gravitational attraction
between any two
objects is directly
proportional to the
product of the masses
of the objects, and
inversely proportional
to the square of the
distance between their
centres.
Units:
F (N)
m (kg)
r (m)
G (N.m2/kg2 )
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where G is a constant
G = 6.67 x 10-11 N.m2/kg2
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Used to determine the Universal Gravitational
Constant, G
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What causes the Ocean tides?
How do scientists decide where satellites
should orbit Earth?
1)
Copy and complete the following chart.
Assume that the same object is used on each
of the three planets.
Planet
Mass on
Planet’s
surface (kg)
Force of
Gravity on
this mass
(N)
g (N/kg)
a) Mercury
57
188
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b) Venus
---
462
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c) Jupiter
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26
2 ) The force of gravity on an astronaut us 600
N at the Earth’s surface. What is the force of
gravity on him at each of the following
distances from the centre of the Earth,
measured in multiples of the Earth’s radius?
(a) 2
(b) 5
(c) 10
(d) 20
3 ) Two of the largest oil tankers in the world,
the Batilus and the Bellaya, have masses of
492 000 t, fully loaded. If they were moored
side by side, 1.0 m apart, their centres would
be 64m apart. Calculate the force of gravity
between them.
4 ) Sirius B is a white dwarf star, in orbit around
Sirius, with a mass of 2.0x 1030 kg, and a
radius of 2.4x107 m.
(a) What is the force on a 1.0 kg mass on the surface
of Sirius B?
(b) What is the acceleration due to gravity on the
surface of Sirius B?
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Static and Kinetic Friction force on Wednesday
Quiz on Friday....
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