7.2 - Balanced forces

Question 1

how are objects described when they are in equilibrium

Answer 1

they are stationary / moving at constant velocity

• all the forces acting ion the object are said to be balanced

Question 2

When is an object at equilibrium when 2 forces are acting on it

Answer 2

when the 2 forces are equal and opposite another

• total resultant force = 0

Question 3

When is an object at equilibrium when 3 forces are acting on it

Answer 3

when the combined resultant force effect of 2 forces is equal and opposite to the 3rd force

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Question 4

how to check if 3 forces acting on an object are balanced

Answer 4

resolve each force along the same parallel and perpendicular lines (splitting them up into components)

balance all the components along each line

Question 5

What does;

S

R

W

F

• stand for in terms of forces

Answer 5

S = support force

R= reactant force

W = weight

F= frictional forces

Question 6

Child on a swing

• break this down into its force components
• state how to work out the tensions components from the angle and other forces give the child is in equilibrium

Answer 6

Question 7

Box on a slope

• break this down into its force components
• how to calculate the force opposing friction and the reactive force

Answer 7

the angle of slope (theta) = angle between mg and mg cos theta

Question 8

practical testing if 3 forces are in equilibria

• diagram (why are pulleys used)
• force diogram

Answer 8

• components of P & Q must create a resultant force = and opposite the force R
• pullies used since they apply 0 resistance forces