P9 Flashcards
What is acceleration?
The rate of change of velocity (in metres per second per second, m/s²).
What is deacceleration?
The rate of change of velocity when an object slows down.
What is displacement
Distance given in a direction
What is the gradient?
Change of the quantity plotted on the y-axis divided by the change of the quantity plotted on the x-axis.
What is the tangent?
A straight line drawn to touch a point on a curve so it has the same gradient as the curve at that point.
What is velocity?
Speed in a given direction (in metres per second, m/s).
Distance-time graph
The gradient of this kind of graph represents the speed of an object.
Vector
A physical quantity that has direction as well as magnitude. e.g. velocity.
Scalar
A physical quantity that has magnitude, but not direction. e.g. speed.
What does S stand for in SUVAT?
Distance travelled
What does U stand for in SUVAT?
Intial velocity
What does V stand for in SUVAT?
Final velocity
What does A stand for in SUVAT?
Acceleration
What does T stand for in SUVAT?
Time taken
Does a distance quantity require a specific direction?
i.e. is it a scalar or vector quantity?
No specific direction is required so it is a scalar quantity.
If an object moves 3 metres to the left and then 3 metres back to its initial position, what is the object’s total displacement?
• The object has zero displacement
• Displacement is a vector quantity so it also involves direction
• The object starts and ends at the same point
State a typical value for the speed of sound
330 m/s
What is a typical value for human walking speed?
1.5 m/s
What is a typical value for human running speed?
3 m/s
What is a typical value for human cycling speed?
6 m/s
State the equation linking distance, speed and time.
Give appropriate units.
Distance = Speed × Time
Distance (m), Speed (m/s), Time (s)
Why can an object travelling at a constant speed in a circle not have a constant velocity? (Higher)
• Speed is a scalar quantity
• Velocity is a vector quantity which means it can only be constant if the direction is constant
• In circular motion, the direction is continuously changing
How can speed be calculated from a distance-time graph?
The speed is equal to the gradient of the graph.
What must be done to calculate speed at a given time from a distance-time graph for an accelerating object? (Higher)
• Drawing a tangent to the curve at the required time
• Calculating the gradient of the tangent
State the equation for the average acceleration of an object. Give appropriate units.
Acceleration = (Change in Velocity)/(Time
Taken)
Acceleration (m/s?), Velocity (m/s), Time (s)
How can the distance travelled by an object be calculated from a velocity-time graph? (Higher)
It is equal to the area under the graph.
Give an approximate value for the acceleration of an object in free fall under gravity near the Earth’s surface.
9.8 m/s?
What can be said about the resultant force acting on an object when it is falling at terminal velocity?
• The resultant force is zero
• When at terminal velocity, the object is moving at a constant speed and so isn’t accelerating
State Newton’s first law for a stationary object.
If the resultant force on a stationary object is zero, the object will remain at rest.
State Newton’s first law for a moving object.
If the resultant force on a moving object is zero, the object will remain at constant velocity (same speed in same direction).
What can be said about the braking forces and driving forces when a car is travelling at constant velocity?
The braking forces are equal to the driving forces.
If an object changes direction but remains at a constant speed, is there a resultant force?
Since there is a change in direction, there is a change in velocity and so there must be a resultant force.
