3.2 Flashcards
What is Newton’s first Law
An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
What is Newton’s third Law?
For every action, there is an equal(in size) and opposite reaction.
What is Newton’s second law?
F = change in momentum/ change in time
What is the definition of the Newton?
The force that will produce an acceleration of 1m/s^2 when it acts on an object of mass 1kg
Explain how you can use a plumbline to find the centre of mass of a piece of card.
Hang object up so that it is free to swing without obstruction
Hang a plumbline from the same suspension point
Mark the vertical line directly below the suspension point.
suspend object from a different location within the object
Again, hang a plumb line to determine the vertical and mark it on
The point at which the two marked lines cross is the centre of mass
Describe what happens when a resultant force F acts on a body with mass m
The body will accelerate in the direction of the resultant force. the resultant force is related to mass and acceleration by the formula:
F=ma
What is meant by drag
An object moving through a fluid experiences a drag force acting on it. Drag is a frictional force that opposes motion. In air this is air resistance.
What is meant by terminal velocity?
When the forces acting on the falling object become balanced so the resultant force is 0. The acceleration becomes zero and the object is moving at max velocity.
What is the principle of moments?
For an object in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments.
what is a moment?
A turning force:
F x perpendicular distance
What is meant by a couple?
A pair of equal and opposite coplanar forces that have equal magnitude and opposite direction, applied to a body parallel to each other but not along the same line.
For a uniform object, where is the centre of gravity?
At the geometric centre of the object.
What is meant by density?
The mass per unit volume of a substance. The unit is kgm^-3
What is meant by pressure?
the pressure is the normal force exerted on a surface per unit area. It is measured in Pascals(Pa), where 1 Pa = 1 Nm^-2.
What is the force that an object submerged in a fluid experiences?
It experiences an upwards force called upthrust. This is because the pressure at the bottom surface of the object is greater than at its top surface.
