4.5.1.4 Resultant Forces Flashcards
(9 cards)
What is a resultant force?
A single force that has the same effect as all the original forces acting together on an object. It replaces multiple forces with one equivalent force.
How do you calculate the resultant force when forces act in a straight line (same or opposite direction)?
Same direction: Add the forces.
Opposite direction: Subtract the smaller from the larger.
The direction of the resultant is the same as the larger force.
What is a free-body diagram? (HT only)
A diagram showing all the forces acting on an isolated object or system. Forces are represented as arrows, where:
Direction shows direction of force
Length shows magnitude (relative)
In a free-body diagram, how can you tell if forces are balanced? (HT only)
If the resultant force is zero, the object is in equilibrium — this means all forces cancel out, and the object is either stationary or moving at constant velocity.
What does it mean to resolve a force? (HT only)
To split a single force into two perpendicular components (usually horizontal and vertical) that have the same effect as the original force.
How are forces resolved in vector diagrams? (HT only)
Draw the force vector to scale.
Create a right-angled triangle using horizontal and vertical components.
Use scale drawings or trigonometry (e.g. SOHCAHTOA) to calculate components or magnitude.
Q: What does it mean when an object is in equilibrium in terms of vectors? (HT only)
All the forces on the object combine to zero, both in magnitude and direction. In a vector diagram, the arrows form a closed triangle or polygon, indicating balance.
Example: A force of 50 N acts at an angle of 30° above the horizontal. What are the horizontal and vertical components? (HT only)
Horizontal:
�
�
=
50
cos
(
30
∘
)
≈
43.3
�
F
x
=50cos(30
∘
)≈43.3N
Vertical:
�
�
=
50
sin
(
30
∘
)
≈
25.0
�
F
y
=50sin(30
∘
)≈25.0N
Why are free-body diagrams useful in problem solving? (HT only)
They allow you to visualise all forces acting on an object, helping identify whether the object will accelerate, remain in equilibrium, or change direction.
