The point where the mass of an object is thought to be concentrated
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Explain how you find the centre of mass of an object.
You suspend the object from a string held in a clamp stand. You hang the plumbline from the same pin and mark the position of it on the object. Hang the object from another point and repeat. The centre of mass is where the two lines cross.
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If someone sits in the centre of a seesaw the moment about the pivot is zero. Why?
Because their perpendicular distance to the pivot is zero.
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How do you increase the stability of an object?
Have a wider base and lower centre of mass.
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What is the equation for pressure?
Pressure = force (N) ~ cross sectional area at a right angle to the direction of the force (m )
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What properties of a liquid make it useful in a hydraulic system?
They are incompressible and the pressure is transmitted equally in all directions.
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What is centripetal acceleration?
When an object moves in a circular motion so constantly changes velocity.
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What is centripetal force?
The resultant force that acts on an object to make it accelerate.
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What happens to the bob if the string breaks in circular motion?
It will move straight at a tangent to the circle.
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How do you increase centripetal force?
By increasing the mass of the object, speed of the object and radius of the circle.
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What is an example of oscillating motion?
A pendulum moving to and fro along the same line.
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What is the amplitude of an oscillation?
The distance from equilibrium to the highest position on either side.
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What does the time period of a simple pendulum depend on?
The length of the string.
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What is the moment of a force?
The turning effect of a force.
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Why is it easier to move an object with a lever than with your hands?
A lever allows you to apply the same force at a greater distance from the pivot, giving a bigger moment.
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Why must an object moving in a circle be accelerating?
It is continuously changing direction so is continuously changing velocity.
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An object that is freely suspended is displaced slighty then let go. Where will its centre of mass be when it comes to rest?
Directly below the point of suspension.
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Why will an oscillating simple pendulum eventually come to rest?
It transfers energy doing work against friction at the pivot and air resistance.
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When will an object topple over?
When the line of action of its weight is outside its base.
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Other cards in this set
Card 2
Front
Explain how you find the centre of mass of an object.
Back
You suspend the object from a string held in a clamp stand. You hang the plumbline from the same pin and mark the position of it on the object. Hang the object from another point and repeat. The centre of mass is where the two lines cross.
Card 3
Front
If someone sits in the centre of a seesaw the moment about the pivot is zero. Why?
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