3. FORCES AND NEWTONS LAWS Flashcards
1
Q
- What is the definition of a force?
A
- a force is a measurable influence that causes something to move
2
Q
- What is Force fundamentally?
A
- it is anything that is measurable
- and causes a change in the motion of an object
3
Q
- What is Newtons First Law?
A
- Newton’s first Law states that any object continues at rest, or at constant velocity, unless an external force acts on it.
- this external force can be a net or resultant force
4
Q
- What gives an object acceleration?
A
- an external force that acts on the object
5
Q
- Give two points about the acceleration produced by an external force acting on an object?
A
- the acceleration is proportional to the force applied
- it is also inversely proportional to the force over the mass
6
Q
- State Newton’s 2nd Law?
A
- when a Net Force acts on an object with mass (m), the object will accelerate in the direction of the Net Force
7
Q
- What is the equation for Newton’s 2nd Law?
A
- F=ma
8
Q
- What is the SI unit of Force?
A
- a Newton (N)
9
Q
- What is the definition of a Gravitational Field?
A
- it is the force acting per unit of mass
10
Q
- What is the definition of Weight (Fg)
A
- this is the Gravitational Force that the Earth exerts on any object on or near its surface
11
Q
- What is the direction of the Gravitational Force that acts on an object?
A
- downwards towards the centre of the Earth
12
Q
- How does one work out the weight of an object?
A
- W= mg
- g= 9.81 m/s2
13
Q
- Is the weight of an object Force or Mass?
A
- it is a force
14
Q
- What value does one see when they measure themselves on a bathroom scale?
A
- we see our mass in kg
- this is the same as our Weight in Newtons, with one zero being removed
15
Q
- When an object is at rest, is there a gravitational force acting on it?
If so, why?
A
- Yes
- the gravitational force on the object does not disappear
16
Q
- When there is a Gravitational Force acting on an object, does the object move?
If not, why?
A
- NO
- this is due to Newton’s 2nd Law
- the net force of an object at rest is Zero
- this means that there is another force balancing out the gravitational force acting on the object
17
Q
- What is the name of the force that balances out the Gravitational Force when an object is at rest?
A
- the Normal Force
18
Q
- What kind of force is a Normal Force?
What does this entail?
A
- it is a contact force
- it means that this force occurs when one object is in contact with another
19
Q
- Provide the definition and the symbol of a Normal Force?
A
- the perpendicular force exerted by a surface on an object in contact with it
- Symbol: FN
20
Q
- What does Newton’s Third Law State?
Provide 2 points.
A
- it states that Forces come in pairs
- for every force that is applied to a body, there is a force applied by that body
21
Q
- Provide a definition for Newton’s 3rd Law?
A
- when Object A exerts a force on Object B, Object B simultaneously exerts an oppositely directed force of equal magnitude on Object A
22
Q
- What does the “Action” Force refer to?
A
- it is the force applied by one object on another object
23
Q
- What is the counterpart force to the “Action” Force?
A
- the reaction force
24
Q
- Do Action and Reaction forces act on the same object?
A
- NO
- they act on different objects
25
25. Answer the following question?
- the Fg and the FN force are acting on the same object
- this does not abide with Newton's 3rd Law
- In order for Newton's 3rd Law to be acceptable, the action and reaction forces need to be acting on different objects
26
26. What are the 4 Fundamental Forces?
- Electromagnetic Forces
- Gravitational Forces
- Strong Nuclear Forces
- Weak Nuclear Forces
27
27. What are the 3 Derived Forces?
- Normal Force
- Tension Force
- Friction Force
28
28. What is a Tension Force?
- the force that is exerted on an object by a cord (rope/cable/etc) that is attached to the object and pulled tightly
- the cord pulls on the object with a force that is directed away from the body and along the cord
29
29. Why is this force called a Tension Force?
- the cord is said to be under tension
- or in a state of tension
30
30. What are the 2 assumptions about the Chord when we are talking about Tension Force?
- it is massless
- it is unstretchable
31
31. What does Massless mean?
- the mass of the chord is negligible (unimportant) compared to the mass of the object it is acting on
32
32. What does Unstretchable mean?
- the cord exists only as a connection between 2 objects
- it pulls on both objects with the same force magnitude (T)
33
33. What is Frictional Force?
- the resistance to the object's movement by a bonding between the object and the surface
34
34. Provide a definition for Frictional Force (due to a surface) and the symbol for it.
- The force that opposes the motion of an object AND acts parallel to the surface with which the object is in contact
- it acts in the opposite direction of the intended motion of the object
SYMBOL: Ff
35
35. Provide a definition for Static Friction.
- it is the frictional force on a stationary object that opposes the tendency of motion of the object
36
36. What is the maximum static friction?
- the magnitude of the Static Friction will increase from 0N
- this happens as the Fg// increases
- this happens until the maximum static friction is reached
- this is the magnitude of the friction when the object just begins to move
37
37. What is kinetic Friction?
- it is the frictional force on a moving object that opposes the motion of the object.
38
38. What is the general formula to calculate the coefficients of Friction?
f= uN
39
39. What is the formula for max static friction?
40
40. What is the formula for Kinetic Friction?
41
41. What can be said about the magnitudes of the coefficients of static and kinetic friction?
- the coefficient of kinetic friction is always smaller than the coefficient of static friction
42
42. Read through this summary, do you understand it?
- Yes
43
43. Read through this summary, do you understand it?
- Yes
