Energy and motion Flashcards
What is mass?
Mass is the amount of matter in an object. This always stays the same
What is weight?
Weight is the effect of gravity on mass. This changes depending on the strength of the gravitational force
What is resultant force?
Overall force on a point or object
What is the resultant force of a stationary object?
0N, as the forces are balanced
What does a resultant force mean?
A change in velocity (acceleration) in that direction (could be starting, stopping, speeding up, slowing down or changing direction)
What does no resultant force mean?
No change in velocity (no acceleration)
What does an object need to start moving?
A force
What happens when two objects interact?
The forces they extend on each other are equal and opposite
What is friction?
A force that acts in the opposite direction to movement
When does friction occur?
Between two objects in contact
What is friction called in fluids?
Resistance or drag
How can you reduce drag?
By streamlining objects
What happens when speed increases?
Friction also increases
What is terminal velocity?
The maximum speed of a falling object that is reached when the weight and resistance are balanced
Explain one example of terminal velocity
Parachute example:
- At first, the parachutist’s weight is greater than resistance so it accelerates downwards
- As speed increases, resistance so the forces balance, so they fall at terminal velocity
- The parachute opens, increasing surface area and resistance, so they decelerate downwards
- As speed decreases, resistance decreases until the forces balance, so they are at a lower terminal velocity
