Topic 2 - Motion and Forces

Created by

Marissa moor

Cards (49)

What is a scalar quantity?
A quantity that has only magnitude
A quanity that isnt direction dependent
What is a vector quantity?
a quantity that has both magnitude and an associated direction
How can a vector quantity be represented?
Using vector arrows.
How do vector arrows represent vectors?
● The length of the arrow represents the magnitude
● The arrow points in the associated direction
Give three examples of vector quantities
1. Velocity
2. Displacement
3. Force
Give examples of scalar quantities
● Temperature
● Time
● Mass
● Speed
● Distance
● Energy
What is velocity? 
the speed of an object in a particular direction
Give an equation relating average speed, distance and time
average speed = distance / time
On a distance/time graph, what value does the gradient of the line represent?
The speed
On a displacement/time graph, what value does the gradient of the line represent?
The velocity
What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?
● 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/s²), Velocity (m/s), Time (s)
Give an equation relating final velocity with initial velocity, displacement and acceleration. 
v² = u² + 2as
How can the distance travelled by an object be calculated from a velocity-time graph?
It is equal to the area under the graph.
On a velocity/time graph what does the gradient of the graph represent?
acceleration
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
Give an appropriate value for the acceleration of an object in free fall under gravity near the Earth's surface.
10 m/s2
What is the name given to the single force that is equivalent to all the other forces acting on a given object?
resultant force
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 a constant velocity (same speed in the same direction)
State the equation for Newton's second law.
Resultant force = Mass x Acceleration
F = ma
State Newton's second law in words.
An object's acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass.
What is weight? 
The force that acts on an object due to gravity and the object's mass.
What quantities does weight depend on?
Weight = mass x gravitational field strength
● The object's mass
● The gravitational field strength at the
given position in the field
What is the unit used for weight?
The Newton (N)
What is the unit used for gravitational field strength? 
N/kg
What piece of equipment can be used to measure an object's weight?
A calibrated spring-balance or newton- meter.
When can an object travelling at a constant speed not have a constant velocity?
When the object is changing direction; for example, moving in a circle.
Why does an object travelling at a constant speed in a circle not have a constant velocity?
● 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
● Velocity is constantly changing
What is the resultant force that acts on an object moving in a circle called, and in which direction does it act?
It is called the centripetal force and acts towards the centre of the circle.
What is inertial mass?
● A measure of how difficult it is to change a given object's velocity
● The ratio of force over acceleration
State newton's Third Law. 
Whenever two objects interact, the forces that they exert on each other are always equal and opposite.
State the equation used to calculate an object's momentum.
Momentum = mass x velocity
What is the unit used for momentum?
kgm/s
kilogram metres per seconds
In a closed system, what can be said about the momentum before and after a collision?
The total momentum before is equal to the total momentum afterwards.
State an equation linking change in momentum, force and time.
Force x Time = Change in Momentum
F Δt = PF Δt = mΔv
How can you measure human reaction times?
● Using the ruler drop test
● Person A and B hold each end of a ruler with the 0 cm mark at the bottom
● Person A drops the ruler without telling person B
● Person B catches it
● The distance travelled corresponds to their reaction time