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Definition
A body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state.
hint - in dirt it will stay put unless dug up |
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Definition
A force applied to a body causes acceleration of that body
• of a magnitude proportional to the force
• in the direction of the force
• and inversely proportional to the body’s mass
f=ma
Hint: magnitude direction inversely proportinal
Accel program- MDI
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Definition
•For every action, there is an equal and opposite reaction.
• When one body exerts a force on a second, the second body exerts a reaction force that is equal in magnitude and opposite in direction on the first body. |
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In accordance with the law of reaction, the weight of a box sitting on a table generates a
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reaction force by the table that is equal in magnitude and opposite in direction to the weight. |
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Definition
A force acting over the area of contact between two surfaces
• direction is opposite of motion or motion tendency
• magnitude is the product of the coefficient of friction (m) and the normal reaction force (R)
F = mR
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| static(motionless) bodies, friction is |
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Definition
| equal to the applied force. |
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| For dynamic bodies (in motion), friction is |
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Definition
constant and less than maximum static friction. |
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Definition
•quantity of motion possessed by a body
• measured as the product of a body’s mass and its velocity;
M = mv |
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| What is the principle of conservation of momentum |
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Definition
In the absence of external forces, the total momentum of a given system remains constant.
M1 = M2
(mv)1 = (mv)2 |
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Definition
impulse: the product of a force and the time interval over which the force acts
Ft |
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Definition
a collision characterized by:
• the exchange of a large force
• during a small time interval |
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| What happens following an impact? |
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Definition
This depends on:
• the momentum present in the system
• the nature of the impact |
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| What happens during impact |
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Definition
This is described by the coefficient of restitution, a number that serves as an index of elasticity for colliding bodies; represented as e. |
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what does the
coefficient of
restitution (e)
describe? |
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Definition
relative velocity after impact
-e = relative velocity before impact
v1 - v2
-e = u1 - u2 |
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| The differences in two balls’ velocities before impact is |
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Definition
| proportional to the difference in their velocities after impact. |
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| . The factor of proportionality is |
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Definition
is the coefficient of restitution. |
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Definition
•in which the velocity of the system is conserved; (e = 1) |
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Definition
•- in which there is a total loss of system velocity;
(e = 0) |
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| Most impacts fall in between |
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Definition
•perfectly elastic and perfectly plastic. |
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Definition
•the product of a force applied against a resistance and the displacement of the resistance in the direction of the force
W = Fd
• units of work are Joules (J) |
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Definition
•the rate of work production
• calculated as work divided by the time over which the work was done
W
P = t
• units of work are Watts (W) |
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What is mechanical energy? |
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Definition
•the capacity to do work
• units of energy are Joules (J)
• there are three forms energy:
• kinetic energy
•potential energy
•thermal energy |
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Definition
•energy of motion
KE = ½mv2 Hint- ken can move
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What is potential energy? |
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Definition
•energy by virtue of a body’s position or configuration
PE = (wt)(ht) |
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What is the law of conservation of mechanical energy? |
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Definition
When gravity is the only acting external force, a body’s mechanical energy remains constant.
KE + PE = C
(where C is a constant - a number that remains unchanged) |
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What is the principle of work and energy? |
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Definition
The work of a force is equal to the change in energy that it produces in the object acted upon.
W = DKE + DPE + DTE
(where TE is thermal energy) |
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