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Flashcards in Physics Deck (128)
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What is a distance time graph?

A graph to help us describe the motion of an object.


What does the gradient of a distance-time graph represent?

The speed of the object.
The steeper the gradient, the greater the speed.


How do we work out speed?

Speed = distance / time

m/s = m / s


What is the speed of an object?

The distance travelled each second.


What does a horizontal line on a distance-time graph mean?

The object is stationary.


What does a straight vertical line on a distance time graph mean?

The object is moving at a constant speed.


What is the speed of a runner who covers 400m in 50 s?

8 m/s


What is velocity?

The velocity of an object is it's speed in a given direction.
If an object changes direction it changes velocity, even if it's speed stays the same.


What do we call the change in velocity?



What is the unit for acceleration?

m/s 2


What is the equation to work out acceleration?

Acceleration = (final velocity - initial velocity) / time
A = V - U / T

m/s 2 = m/s - m/s / s

(V - U also means change in speed)


What happens if the value for acceleration is negative?

It's decelerating or negatively accelerating.


What does a horizontal line on a speed-time graph mean?

A steady, constant speed.


What does a stationary object look like on a distance-time and speed-time graph?

D.T. - a horizontal line

S.T. - no line at all


What does a constant acceleration look like on a distance-time and speed-time graph?

D.T. - an upwards curve (which goes right then up)

S.T. - a positive, straight line


What does steady deceleration look like on a distance-time and speed-time graph?

D.T. - a downwards curve (which goes up then right and stays horizontal)

S.T. - a negative, straight line


What does an object going backwards at a constant speed look like on a distance-time and speed-time graph?

D.T. - a straight, negative line

S.T. - a horizontal line


What does an object constantly accelerating backwards look like on a velocity and speed-time graph?

S.T. - a positive, straight line

V - a negative, straight line


What is acceleration?

Change of velocity per second


What does the area under the line (between the line and the x axis) represent in a velocity time graph?

Distance travelled.


What does the gradient of a velocity time graph mean?

The steeper the line, the greater the acceleration. If the line is horizontal, there is no acceleration so it's travelling at a constant speed.


What does calculating the gradient of a D.T and S.T graph tell us?

D.T. - speed
S.T. - acceleration


What is average speed of a car that travels 1.2 km in 1 minute?

1.2 km = 1200 m
1 minute = 60 seconds

1200m / 60s = 20

20 m/s


What are action and reaction forces?

Objects always exert equal and opposite forces on each other.
If object A exerts a force on object B, object B exerts an equal and opposite force on object A.
These are called action and reaction forces.


What is the resultant force?

The single force that would have the same effect on the object as all the original forces acting together.
The combined effect of all forces acting upon an object.

A resultant force always causes an acceleration so if there's no acceleration, the resultant force must be 0.

The bigger the resultant force, the greater it's acceleration.
The greater the mass of an object, the smaller it's acceleration for a given force.

A resultant force always causes acceleration.The greater the resultant force on an object is the greater its acceleration. The big of a mass of an object the bigger the force needed to give it a particular acceleration


If there are 3 cars
1) driving force 200N - resistance force 200N
2) driving force 300N - resistance force 200N and
3) driving force 100N - resistance force 200N

which car would start moving?

Car 2 as the driving force is greater than the resistance force.


What is the resultant force of a 4N force and a 3N force acting in the same direction?



What is the equation for force?

Force = mass x acceleration

F = m x a

N = kg x m/s 2


Which object has the greatest force acting upon it?
A 5kg rock accelerating at 3 m/s 2 or a 7kg boulder accelerating at 2 m/s 2?

N = kg x m/s 2

1) N = 5 x 3
N = 15

2) N = 7 x 2
N = 14

A 5 kg rock a" at 3 m/s 2 has the biggest force.


What is the stopping distance?

The stopping distance if a vehicle is the distance it travels during the driver's reaction time (the thinking distance) plus the distance it travels under the braking force (the braking distance).

Stopping distance = thinking distance + braking distance