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
Q
- Answer the following question?
A
- 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
Q
- What are the 4 Fundamental Forces?
A
- Electromagnetic Forces
- Gravitational Forces
- Strong Nuclear Forces
- Weak Nuclear Forces
27
Q
- What are the 3 Derived Forces?
A
- Normal Force
- Tension Force
- Friction Force
28
Q
- What is a Tension Force?
A
- 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
Q
- Why is this force called a Tension Force?
A
- the cord is said to be under tension
- or in a state of tension
30
Q
- What are the 2 assumptions about the Chord when we are talking about Tension Force?
A
- it is massless
- it is unstretchable
31
Q
- What does Massless mean?
A
- the mass of the chord is negligible (unimportant) compared to the mass of the object it is acting on
32
Q
- What does Unstretchable mean?
A
- the cord exists only as a connection between 2 objects
- it pulls on both objects with the same force magnitude (T)
33
Q
- What is Frictional Force?
A
- the resistance to the object’s movement by a bonding between the object and the surface
34
Q
- Provide a definition for Frictional Force (due to a surface) and the symbol for it.
A
- 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
Q
- Provide a definition for Static Friction.
A
- it is the frictional force on a stationary object that opposes the tendency of motion of the object
36
Q
- What is the maximum static friction?
A
- 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
Q
- What is kinetic Friction?
A
- it is the frictional force on a moving object that opposes the motion of the object.
38
Q
- What is the general formula to calculate the coefficients of Friction?
A
f= uN
39
Q
- What is the formula for max static friction?
A
40
Q
- What is the formula for Kinetic Friction?
A
41
Q
- What can be said about the magnitudes of the coefficients of static and kinetic friction?
A
- the coefficient of kinetic friction is always smaller than the coefficient of static friction
42
Q
- Read through this summary, do you understand it?
A
- Yes
43
Q
- Read through this summary, do you understand it?
A
- Yes
