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Intro to Physics
What is the work of a force ?
SCALAR value
when a force applied on a body causes its displacement in the direction of the force
expressed in joules (J).
What is the formula for the work of a force ?
What is the formula for the work of a weight ?
(If the body displaces upward, the work is - ; in the opposite case, the work is +)
What is the work of a spring force ? (Write the demonstration of the formula with Hook’s Law)
When stretching or compressing a spring, the displacement of the body is always opposite to the force in the spring (restoration force).
What is the Work of a couple ? (Formula)
What is the kinetic energy ?
A body develops a kinetic energy when it translates at a linear velocity and rotates at an angular velocity.
Kinetic energy is a positive scalar quantity & expressed in joules (J).
What is the Kinetic energy formula when the body rotates about a fixed pivot ?
(If the motion of the body is pure translation, it is sufficient to set in equation)
What is a conservative force ?
It’s when the work of a force depends only on the initial and final positions of the body (so independent of the shape of the path).
What is potential energy ?
It is the energy developed by a conservative force quantifying the ability to change the position of the body with respect to a reference level line called “datum.”
What is the expression of the gravitational potential energy ?
Gravitational potential energy is the work required to move an object vertically in a gravitational field.
What is the elastic potential energy ?
This is the energy stored in an elongated or compressed spring needed to be used as work to return the spring to its unstretched position (datum).
Whar is the expression of the mechanical force ?
What is the expression linking kinetic energy and the sum of works done by all external forces ?
What is the law of conservation of energy ? (show demonstration)
What is the expression of power ?
Give me the simplified expression of power (show demonstration)
What is the other expression of power (using the torque) ? (show demonstration)
Why is some power lost ?
Friction: Energy is dissipated as heat at moving parts and contacts.
Air resistance: Losses due to drag forces.
Material inefficiencies: Internal energy losses within the machine (e.g., electrical resistance in wires or mechanical inefficiencies in bearings).
What is the efficiency formula for power ?
What is linear impulse ? (and its expression)
This is a vector quantity measuring the effect of a force within the time during which this force is applied:
What’s linear momentum ?
The linear momentum of a body is the vector quantity measuring the ability of its matter to translate by a vector velocity of its center of gravity.
Give the expression of the principe of linear impulse and momentum : (and show demonstration)
What can impulsive forces do ?
Impulsive forces have huge magnitudes during very short durations, which are sufficient to cause momentum change.
Do non-impulsive force have any impact ?
Nope, non-impulsive forces are not able to change linear momentum considerably (such as the weight of a system
How can you express the linear momentum of 2 systems balancing each other ?
What happens during impact ?
A large impulsive force will develop between colliding bodies to induce new velocities.
Both particles deform gradually during impact until reaching a maximum deformation status, then they repulse each other.
What’s the resitution phenomenon ?
In the most general case, particles absorb a portion of the momentum to deform and give back the other portion
What is the coefficient of resitution for an elastic impact ?
1
What is the coefficient of restitution for a FULLY plastic impact ?
0
