Class Test December'14 Nat 4 Flashcards
What is speed and what is its units and symbol?
The distance travelled by an object per second, usually measured in metres per second. v
What is average speed of an object and how is it measured?
The average for the whole journey (distance/time)
Measure the distance travelled, measure the time taken, use equation v= d/t
What is instantaneous speed of an object and how is it measured?
Its speed at one particular point during the journey.
Measure the length of the vehicle, measure the time taken to pass a point (light gate) , use equation v=d/t
If the line on a speed time graph is a steeper line (larger gradient), what does this mean?
The greater the acceleration.
What are three things that forces can be detected by?
Change of shape to the object, change of speed to the object and a change of direction of the object
What is friction?
Friction is a resistive force, which opposes the direction of motion of an object. Which means it acts in the opposite direction to motion.
When does friction occur?
When two surfaces make contact.
Air resistance/ air friction/ drag mainly depends on what two factors?
The shape and size of an object, the speed of the moving object.
When does air resistance increase?
It increases as the object accelerates.
Where friction is used to slow down an object, friction should be……?
Increased
Where friction is making movement difficult, friction should be……?
Reduced
What is a balanced force?
Two forces which are equal in size which act in opposite directions. (same as no force at all)
What is weight?
A force caused by gravity acting on an object’s mass. (measured in newtons, N) W=mg
What is mass?
The amount of matter in an object. (measured in kg) m=W/g
