Questions Flashcards
What is terminal velocity ?
The constant velocity that is reached when the drag force (air resistance) equals the force of gravity
Why is a force exerted by a man on a sledge, greater than the force calculated ?
The friction if the sledge on the ground has not been calculated and it would make the force exerted on the sledge greater
What is the difference between a vector and a scalar ?
Similarity : The both have a magnitude
Difference : Vectors have a direction whereas scalers do not
How does the crumple zone of a car help to reduce injuries during a crash
Force = change in momentum ➗ time, therefor if. Momentum is divided by a longer stopping distance made longer by the crumple zone, then the force exerted will be smaller. Therefore if the time it takes a car to change in momentum is slower then there will be a smaller force exerted when it crashes, causing less injury for driver.
Newton’s first law
If no force acts on an object or the forces on it are balanced then it will either remain at rest or move with constant velocity
Eg. Stationary car
Newton’s second law
If an unbalanced force acts on an object then it will accelerate by either speeding up, slowing down, or changing direction
Eg. A car driving fast - where trust > drag
As speed increases what else does ?
Drag force
Explain why the acceleration of a plane is not constant even though the engines produce a constant force
As the plane gets faster the air resistance (drag force) acting upon it becomes greater, eventually becoming greater than the force exerted by the engines, reducing resultant force. Therefore it does not travel at a constant acceleration.
Why does a skater move backwards when she throws a snowball
- conservation of momentum
- momentum of skater and snowball are equal and opposite
- momentum initially zero
Why does a comet travel fastest next to the sun
A comet travels fastest when closest to the sun because it’s gravitational attractions are at their strongest.
What is equal in equilibrium
Sum of clockwise moments = sum of anti-clockwise moments
How far must something be tilted in order to fall over ?
It must be tilted so that’s it’s line of action from its centre of gravity is past the pivot / outside the baseline of the brick
Why would using a longer steel bar to
Ever a tree stump make it easier ?
When the force applied is further from the pivot, it causes an increased moment to act on the steel bar, since moment = f x d. Therefore causing a greater force to act upon the tree
What is centre of mass
The point at which the mass of an object is concentrated
Hooke’s law equation
F = k x e
F = force applied K = spring constant e = extension
