s1w05l2 Force

Gravity g

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Gravity is not a force, but a acceleration

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Gravitational Force is a force.

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acceleration - m\cdot s^{-2}
gravitational field strength - N\cdot m^{-1}

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No resultant force incorrect

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resultant force = 0

Reaction time and distance

factors that affect reaction time

• tiredness
• alcohol/drug use
• any factor that may delay the interpretation of the driver of imminent danger

Factor that affect reaction distance

• reaction time
• velocity
• any factor that may affect time and force

Results of force

Change in motion - Newton’s laws of motion

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1. A body remains at rest, or in motion at a constant speed in a straight line, except insofar as it is acted upon by a force.
2. At any instant of time, the net force on a body is equal to the body’s acceleration multiplied by its mass or, equivalently, the rate at which the body’s momentum is changing with time.
   F = ma = \frac{dp}{dt}
3. For every action, there is an equal and opposite reaction

For Newton’s third law

force must be:

• same type
• act in the same plane but opposite directions
• act on different objects

Change in Shape

Elastic

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you put a force on an object, making the object change shape, and it returns to its original shape after you remove the force

Hooke’s Law

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A material resists with a force proportional to it extension before limit of proportionality
F=k\Delta x
where k is stiffness also spring constant

Limit of proportionality - not proportional but still elastic
Elastic Limit - not elastic

A against/vs/- B means y: A, x: B.
\text{gradient} = \frac{A}{B} = \frac{y}{x}

Inelastic - Plastic

1. vector has directions while scalar doesn’t.
2. they interacted by force
3. According to Newton’s Third Law,  for every action (force) in nature there is an equal and opposite reaction.
4. Gravitational force
5. 200N, up.

1. making it be two forces added together, usually two perpendicular force.
2. all the force adding together is 0
3. C
4. F_{R} = |F_{1}+F_{2}| = 5
5. east

1. F=kx
2. elastic deformation means that the object return to its original shape when there is no more force, while inelastic deformation cannot
3. 1, because A body remains at rest, or in motion at a constant speed in a straight line, except insofar as it is acted upon by a force.
4. k = 25 \ N\cdot m^{-1}, F = kx = 25\times 0.08 = 2\ N
5. k = \frac{F}{x} = \frac{2}{0.11-0.06} = 40\ N\cdot m^{-1}
6. Because he uses the length instead of extension

1. True
2. B
3. when the line turns to a curve, which means they are not proportional
4. spring constant k
5. E_{p} = \frac{1}{2}kx^2 = 25\cdot 0.1^2 = 0.25\ J