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Higher Physics > Our Dynamic Universe > Flashcards

Our Dynamic Universe Flashcards

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1
Q

What objects can the equations of motion be applied to ?

A

The equations of motion can be applied to any object moving with constant acceleration in a straight line.

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2
Q

what are the four equations of motion?

A 
v = u+at ( derived from the acceleration equation)
s = ut + 1/2at^2 
v^2 = u^2 + 2as
s = 1/2 (u+v)t
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3
Q

How do you represent decreasing velocity in an equation of motion?

A

you represent decreasing velocity by use of a negative sign in front of the acceleration value

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4
Q

what are the three graphs of motion that represent Constant “v”?

A

The displacement-time graph (s-t) will be a straight line through the origin
Velocity-time graph should be a straight line above the x axis
The acceleration-time graph should be a straight line on the x axis as there is no acceleration when there is a constant velocity

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5
Q

what are the three graphs of motion for constant acceleration?

A

The displacement-time graph will be a slope upwards as when the acceleration increases constantly the time taken to cover a certain distance will decrease
The velocity-time graph will be a straight line through the origin
The acceleration time graph will be a straight line above the x-axis

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6
Q

what are the three graphs of motion for negative acceleration?

A

the displacement-time graph will be a line that looks a lot like the top left hand quarter of a circle.
the velocity-time graph will be a line with a negative gradient starting high on velocity.
the acceleration time graph will be a straight line UNDERNEATH the x-axis

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7
Q

what do displacement-time graphs represent?

A

Displacement-time graphs represent how far an object is from its starting point at some known time.

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8
Q

What is a velocity-time graph essentially?

A

The velocity-time graph is essentially a graph of the gradient of the displacement-time graph

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9
Q

What is important to consider when drawing graphs of motion?

A

It is important to take care to determine whether the gradient is positive or negative .
(positive slopes UP to the right)
(negative slopes DOWN to the right)

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10
Q

what will all acceleration time graphs you are asked to draw consist of?

A

Straight horizontal lines, all above,below or on the x-axis

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11
Q

What is the area under a velocity-time graph equal to?

A

The displacement of the object that makes the speed-time graph

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12
Q

What is friction?

A

Friction is a resistive force that opposes motion

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13
Q

What is the resultant force?

A

When several forces act on one object they can be replaced by one force which has the same effect. That is the resultant

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14
Q

what is an example of an internal force?

A

The tension in the towbar when a car is pulling a

caravan

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15
Q

how would you find the tension in the towbar when a 700kg car is pulling a 500kg caravan and the car has a constant engine thrust of 3.6kn?

A

Calculate the acceleration of the whole system using F=ma
a=F/m , a=3600/1200 , a= 3ms-^2
Use this acceleration to calculate the tension and use the mass of the caravan only as this is the mass of the object being pulled
T=ma , T=500x3 , T=1500N

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16
Q

What is the tension formula?

A 
T = mg (+/-) ma 
T - Tension 
m - mass
g - gravitational field strength
a - acceleration
17
Q

When dealing with forces on a slope the weight of the object acts in two directions, What two directions?

A

Into the slope (perpendicular)

Down the slope (parallel), making it accelerate down but not at 9.8ms

18
Q

What is the “component” of a force?

A

the amount of force in a given direction

19
Q

How can we find the component of a force?

A

If we have a force in a particular direction, we can use pythagoras and trigonometry to work out the component of a force in a given direction.
COS ACROSS, SIN TO CLIMB

20
Q

what is the equation to find the force down the slope?

A

Fd= mg sin0

0 - theta

21
Q

what is the equation to find the force into the slope?

A

Fi= mgcos0

0 - theta

22
Q

what is the principle of conservation of energy ?

A

Energy cannot be created or destroyed, only converted from one form to another.

23
Q

What can you do with each energy equation?

A

All forms of energy can be converted into any other form, so each of these equations can be equated to any other.

24
Q

What is momentum the measure of?

A

Momentum is the measure of an object’s motion and is the product of mass and velocity
p=mv

25
Q

Is momentum a vector or scalar?

A

Since velocity is a vector so is momentum. this means positive and negative directions are important

26
Q

For what two reasons can an object have a large momentum?

A

A large mass or a large velocity

27
Q

what is the law of conservation of linear momentum?

linear just means in a straight line

A

In the absence of net external forces total momentum before an interaction equals the total momentum after the interaction

28
Q

what is a collision?

A

a collision is an event when two objects apply a force to each other for a relatively short time.

29
Q

Is momentum always conserved when two objects collide?

A

Yes

30
Q

What is a collision called when kinetic energy is NOT conserved?

A

InElastic Collision

31
Q

what is a collision called when kinetic energy is the same before and after the collision?

A

Elastic collision

32
Q

What happens in a simple explosion?

A

In a simple explosion two objects start together at REST then move off in opposite directions.

33
Q

What is different about the momentum in a simple explosion?

A

Momentum must still be conserved, as the total momentum before the is zero , the total momentum after must also be zero. Positive and negative directions are really important
(as the object starts at rest there is no momentum)

34
Q

what is impulse?

A

The product of force and time . When an object experiences an unbalanced force for a short period of time it experiences an impulse. This causes the momentum of the object to change

35
Q

What is the impulse formula?

A

Ft = mv-mu

So Impulse = change in momentum

36
Q

What shape will an impulse graph be in?

A

A triangle

37
Q

How do you find the impulse from a graph?

A

The average force is half of the peak force
Impulse = (1/2 peak force) x t
So impulse is the area under the graph

38
Q

What are the impulse units?

A

Newton seconds (Ns)

39
Q

When drawing an impulse graph what must you be careful of?

A

You must be careful with what force you are given.
If you are given the average force, since the average force is half of the peak force, you must double the average force and put that number on you impulse graph

Higher Physics (9 decks)

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