Mechanics (G) Flashcards
(73 cards)
1
Q
Fc (N)
A
Centripetal force
2
Q
P (kg m s-1)
A
Momentum
3
Q
Pf (Kg m s-1)
A
Final momentum
4
Q
Pi (Kg m s-1)
A
Initial momentum
5
Q
Vf (m s-1)
A
Final velocity
6
Q
Vi (m s-1)
A
Initial velocity
7
Q
r (m)
A
Radius
8
Q
w (J)
A
work
9
Q
T (Nm)
A
Torque
10
Q
F (N)
A
Force
11
Q
m (Kg)
A
Mass
12
Q
ac (m s-2)
A
Centripetal acceleration
13
Q
t (s)
A
Time
14
Q
a (m s-2)
A
acceleration
15
Q
d (m)
A
Displacement (distance)
16
Q
K (Nm-1)
A
Stiffness
17
Q
x (m)
A
Extension
18
Q
Ep (J)
A
Energy stored in a spring
19
Q
mg (m s-2)
A
Gravitational acceleration
20
Q
Calculate the momentum
A
p=mv
21
Q
Ek (J)
A
Kinetic energy
22
Q
Calculate the potential energy stored in a spring
A
Ep=1/2Kx^2
23
Q
Calculate the gravitational potential energy
A
ΔEp=mgΔh
24
Q
Calculate how much energy is transformed per second (work done)
A
P=w/t
25
Calculate centripetal acceleration, velocity, or radius
Fc=mv^2/r
26
Calculate force, mass, or acceleration
Fnet=ma
27
Calculate the energy transfer (work)
w=Fd
28
Calculate kinetic energy
Ek=1/2mv^2
29
Calculate impulse
Δp=FΔt
30
Calculate the torque, force, or distance from the pivot point
T=Fd
31
Calculate the extension or compression of a spring
F=-KX
32
Calculate change in momentum (vector subtraction)
Δp=Pf-Pi
33
Define Impulse
The change in momentum of an object due to a force acting on it over a certain time.
34
Define power
The rate at which work (energy transfer) is done.
35
Equilibrium in relation to forces
When the forces are balanced or the total upwards force equals the total downwards force AND when the torques are balanced or the total anti-clockwise torque equals the clockwise torque.
36
Define centripetal force
Force to the centre of the circle that keeps mass moving in circular motion and creates centripetal acceleration (also to the centre of the circle). This is the net force on a mass moving in circles and can come from tension or friction.
37
How is momentum conserved during a collision?
In collisions we assume the interaction between colliding objects happens so quickly that external forces don't have enough time to significantly change the momentum of the objects. Thus, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.
38
Explain a reaction force
A reaction force is a force that acts in response to an applied force.
39
Define gravitational potential energy
The stored energy that an object has due to its height above the ground.
40
Newtons 1st law
An object maintains constant velocity (including being stationary) unless acted upon by an external net force.
41
Newtons 2nd law
If an object experiences an external net force, it will accelerate proportional to its mass.
42
Newtons 3rd law
When an object exerts force on another object, the object will simultaneously exert an equal and opposite reaction to the force acting upon it.
43
Friction force + examples
The force that can oppose the motion of an object.
E.g. static, kinetic, drag.
44
Net force in relation to acceleration
The force that is remaining after all the forces acting on an object have been added together to give one final force. This force determines the change in motion (acceleration) of an object.
45
What does the arrow length indicate in a vector
Vector quantities are represented by arrows. The length of the arrow represents the magnitude (size) of the quantity.
46
Define kinetic energy
A form of energy that an object has due to its own motion.
47
Define work
The transfer of energy by a force acting on an object as it is displaced.
48
Define force
An influence that acts to accelerate objects. It is measured in Newtons (N).
49
Gravity
(9.8 m s-2)
50
What makes gravity negative or positive
Gravity (g), is like an accelerator and g will be positive if the object is stationary or moving downwards. g will be negative (-9.8) if the object is moving upwards, (away from gravity).
51
Explain Hooke's law
How springs will behave when loads are placed on them - either a stretching or compressing force. When springs are stretched or compressed they produce a restoring force. This force tries to move the spring back to its original position.
52
Define tension force + examples
The force transmitted through a rope, string, or wire when pulled by forces acting from opposite sides.
E.g. tug of war, rock climbing, crane.
53
Explain the concept of equilibrium, where upwards forces equal downwards forces, and clockwise torques equal anti-clockwise torque.
Equilibrium in the context of forces and torque means...
- For forces: The vector sum of all forces in any direction is zero.
- For torques: The sum of all torques around any pivot point is zero.
54
Define torque
Torque is a measure of the force that can cause an object to rotate about an axis, specifically the twisting or turning force that causes an object angular acceleration (rotation around an axis).
55
Difference between an elastic and inelastic collision
Elastic collision: Kinetic energy and momentum are conserved. Objects bounce off each other without sticking or deforming.
Inelastic collision: Kinetic energy is not conserved. Objects may stick together or deform due to the collision.
56
Link the motion of a projectile to the forces acting on it
The motion of a projectile is intricately linked to the forces acting on it:
- Gravitational force, causes vertical acceleration.
- Air resistance, affects both horizontal and vertical motion.
- Initial velocity components, (horizontal and vertical) determine the trajectory shape and dimensions.
57
Difference between mass and weight
Weight is the force of gravity on a mass. Weight is measured in Newtons and has the direction downwards (to earths centre).
Mass has no direction, and is measured in kilograms and is not a force but the amount of matter in an object.
58
Define momentum
Momentum is the product of an objects mass and velocity, specifically "mass in motion" objects with greater mass, or higher velocity, have more momentum and require greater force to stop them.
59
Explain how horizontal velocity stays the same during projectile motion
The horizontal velocity of a projectile remains constant throughout its flight because there are no horizontal forces acting on it, once it has been launched.
60
Explain how an object can travel at a constant speed during its circular motion despite accelerating
Centripetal Acceleration: Changes only the direction of the object's velocity, not its speed.
Constant Speed: The speed (magnitude of velocity) remains constant as long as centripetal force is applied.
Centripetal Force: Keeps the object in circular motion, causing it to accelerate by changing direction but not speed.
Key Concept: An object in circular motion accelerates directionally (centripetal acceleration) while maintaining a constant speed.
61
Describe the size of vertical and horizontal velocity components at the starting point midpoint and endpoint of projectile motion:
Starting Point (Launch):
Vertical Velocity: Depends on initial upward/downward speed.
Horizontal Velocity: Depends on initial sideways speed.
Midpoint (Highest Point):
Vertical Velocity: Zero (momentarily stops moving upward before descending).
Horizontal Velocity: Remains constant (same as at launch, assuming no air resistance).
Endpoint (Returning to Initial Height):
Vertical Velocity: Same magnitude as at launch, but in the opposite direction.
Horizontal Velocity: Remains unchanged from the initial value (assuming no air resistance).
62
Explain why the vertical velocity changes throughout projectile motion
Gravity's Effect: Vertical velocity changes continuously due to gravity (constant downward acceleration).
Ascent: Vertical velocity decreases as the object rises (slows down).
Peak: Vertical velocity = 0 (momentary stop before descending).
Descent: Vertical velocity increases (accelerates downward) as the object falls back.
63
Explain how the impulse equation is useful for investigating the damage from a collision
Key Concept: Impulse relates the force exerted over a period of time to the change in momentum of an object.
Collision Analysis: Useful in quantifying the force during a collision, helping assess potential damage or injury.
Application: Helps explain how larger forces over shorter times can cause more damage, directly linking force, time, and injury potential in collisions.
64
Explain the relationship between torque, the size of the force, and the distance from the pivot point.
Force Magnitude: Larger force = greater torque, if applied perpendicular (90°) to the lever arm.
Lever Arm Length: Torque increases with distance from the pivot point (longer lever arm = more torque).
Key Concept: The magnitude of force and distance from the pivot both affect torque.
65
Why is energy lost when converted from potential to kinetic energy? And what type of energy is lost.
Law of Conservation: Energy cannot be created or destroyed, only transformed.
Potential to Kinetic: As an object falls, its potential energy is converted into kinetic energy.
Total Mechanical Energy: Stays constant in an isolated system (sum of potential and kinetic energy).
Energy Transformations:
Heat: Kinetic energy converts into heat due to air resistance or friction.
Sound: Energy can be transformed into sound from air displacement or collisions.
66
Explain how the velocity of an object is tangential (90°) to centripetal force
Centripetal Force: Acts towards the center of the circular path.
Key Role: Responsible for changing the direction of the object's velocity, keeping it in a curved path.
67
Balanced forces in relation to acceleration
Definition: Forces that are equal in magnitude and opposite in direction.
Effect on Object: No acceleration; the object will remain stationary or continue at a constant velocity.
68
Compare the effect of balanced and unbalanced forces on the direction, velocity, and acceleration of an object
Balanced Forces: Maintain the object’s current state of motion (either at rest or moving with constant velocity).
Unbalanced Forces: Cause a change in motion (change in velocity and/or direction) due to acceleration in the direction of the net force.
69
Scaler Quantities
Has a size but doesn't have a direction, e.g. time
70
Vector Quantites
Has a size and a direction, e.g. velocity
71
Conservation of energy rules
The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another. This means that a system always has the same amount of energy, unless it's added from the outside.
E.g. If someone is bouncing off a spring board, we know that all of the elastic potential energy will be converted to kinetic energy, as soon as the person leaves the board (jumps into the air).
72
Kinetic energy
The energy an object has because of its motion. I.e energy which a body possesses by virtue of being in motion.
73
Requirements for equilibrium, e.g. state the conditions required for for a bridge to be in equilibrium...
No net forces
and
No net torques
