| Vectors have both ? | Magnitude and direction |
| When adding 2 or more forces that act in a straight line, what must we take into account? | We have to take account of their direction |
| When you draw a scale drawing you should: | 1. State the scale used
2. Draw large diagram to reduce the uncertainty |
| What are the forces that are acting on a trolley on a ramp ? | 1. Wight of the trolley (acts vertically downwards )
2. Contact force of a ramp - acts at right angles to ramp |
| cos(90* - θ) = | sin θ |
| We can work out trolley's acceleration using what formula? | F = mg sinθ |
| Define centre of gravity? | the point where all the weight of the object may be considered to act |
| Forces can have turning effect, what does this mean? | they can make an object turn around |
| Moments of a force depends on what 2 quantities? | 1. Magnitude of the force
2. Perpendicular distance of a force from a pivot |
| What is the formula for calculating moment of a force? | Moment of a force = force x perpendicular distance |
| What are the 2 methods to calculate the moment of the force
{1(5)}
{2(4)} | 1
Draw a perpendicular line from the pivot to the line of a force
Find distance x`2
Calculate moment of force = F`2 x x`2
From the right angle triangle we can see that :
x`2 = d sin θ
Moment of force = F`2 x d sin θ = F`2 d sin θ
2
Calculate component of F`2 that is at 90° to the lever
F`2 sin θ x d
Moment of a force = F`2 d sinθ |
| We can use the moment of a force to solve two sorts of problems? | 1. Check whether an object will remain balanced or state to rotate
2. Calculate an unknown force or distance if we know that an object is balanced |
| What does the principle of moments state? | The principle of moments states that, for any object that is in equilibrium, the sum of the clockwise moments about any point provided by the forces acting on the objects equals the sum of the anticlockwise moments about the same point |
| Think about a car steering wheel. The 2 forces balance up and down, so the wheel does not move up down or sideways
1. Is the wheel at equilibrium
2. What will the pair of forces cause to happen?
3. What are the pair of forces known as? | 1. The wheel is not in equilibrium
2. The pair of forces will cause it to rotate
3. Couple |
| A couple has a turning effect, but does not cause an object to accelerate. To form a couple, the two forces must be:...(3) | 1. Equal in magnitude
2. Parallel but opposite in direction
3. Separate by distance d |
| What is known as torque | The turning effect or moment of a couple is known as its torque |
| The torque of a couple is known defined as follows: | torque of a couple = one of the forces x perpendicular distance between the forces |
| For an object to be in equilibrium, 2 conditions must be met at the same time? | 1. The resultant force acting on the object must be zero
2. The resultant moment is zero |
