Motion Flashcards
What is the equation for speed?
Speed in m/s is distance travelled s ( m ) / time taken T (Seconds)
What does the gradient of a line on a distance-time graph represent?
Speed
What do tachographs do?
They measure how long a vehicle user has been driving
What is velocity?
Speed in a given direction
Why does an object moving in a circle have a velocity that isn’t constant, even if it’s speed is?
Because it is constantly changing direction.
What is displacement?
Distance travelled in a given direction
what is acceleration?
The change in velocity of a moving object per second
what is the equation for acceleration?
Change in velocity as m/s / time taken for the change (seconds)
How do you work out change in velocity?
final velocity - initial velocity
What is Deceleration?
The change of velocity per second when an object slows down.
What is a vector?
A physical quantity that has direction as well as magnitude. ( eg velocity)
What is a scalar?
A physical quantity that has magnitude but not direction. (eg speed)
What does the gradient of the line on a velocity- time graph represent?
Acceleration
What does the gradient of a line on a distance-time graph represent?
Speed
what is the equation for resultant force?
resultant force F ( newtons, N) = mass (kg) x acceleration (m/s2)
What is Newtons second law of motion?
that the acceleration of an object is proportional to the resultant force on the object and inversely proportional to the mass of the object
What is Inertia
The tendency of an object to stay at rest or in uniform motion (not changing)
What happens to resultant force with acceleration?
The velocity increases - if the resultant force is in the same direction as the velocity = what makes it positive
What happens to resultant force with deceleration?
The velocity decreases - if the resultant force is in the opposite direction as the velocity = what makes it negative
What is the equation for acceleration, using force and mass?
acceleration m/s2 = force N x Mass Kg
What is the weight of an object?
The force acting on it due to gravity and measured in newtons
what is the mass of an object?
Depends on the quantity of matter in it. KG.
what is the equation for weight?
weight N = mass kg x gravitational field strength ( 9.8N/kg for the earth)
What is terminal velocity?
The velocity it reaches when it is falling. At that point, the weight is equal to the friction on the object.
What is the resultant force, if the object is moving at terminal velocity?
zero
Why is a car’s resultant force zero if it travels at a constant velocity?
Because the driving force of it’s engine is balanced by the resistive forces, which are mostly caused by air resistance.
Which 2 factors affect breaking force?
the speed when breaks are applied and the mass of the vehicle
what is the equation for resultant force?
resultant force = mass x acceleration
What makes up the total stopping distance of a car?
thinking distance (how long it takes to react) + breaking distance (the distance travelled when breaking and trying to stop)
Name 4 factors that affect breaking distance
- tiredness and alcohol (increased reaction time)
- Speed (thinking and breaking distance increased)
- weather and road conditons ( increases breaking distance)
- poorly maintained cars ( increased breaking distance)
What is momentum?
Momentum is the product of an object’s mass and velocity. It is a measure of how much motion an object has and how difficult it is to stop.Momentum is a vector quantity, meaning it has both size and direction.
What is the equation for momentum?
momentum kg / m/s= mass x velocity
What is the conservation of momentum?
In a closed system the total momentum before an event is the same as the total momentum after the event. This assumes no external forces are interfering.
What factors affect a vehicle’s collision?
The force of the impact of the collision depends on mass, change of velocity and the length of impact time.
What happens when impact time is increased?
The impact force is reduced.
What happens in terms of forces when two vehicles collide?
They exert equal and opposite forces on each other and their total momentum is unchanged.
How do we calculate impact force?
change in momentum / impact time ( so the shorter the impact time, the greater the impact force.
