Chalter 3

Question 1

How do you find a cars true speed, what value you need to take
How do you do this

Answer 1

Have to take instantaelunludnspeed, which means close the time distance as much as you can

Question 2

Distance time graph

Instantaneous speed?

Answer 2

Gradient = speed

Find a Rahmen of a curve and calculated speed here

Question 3

Displacement time graph

Answer 3

Gradient velocity

Question 4

Velocity time graphs

What do shape of lines mean

Answer 4

• gradient = acceleration
• displacement = area under (- area under negative )
  , total distance = total are under

1) if straight then constant velocity
2) if straight up constant increasing velocity
3) if straight up curved = increasing velocity at increasing rate
If curved down = decreasing velocity at increasing rate

Question 5

What gives something infinite acceleration?

Essentially what happens when you change direction to acceleration

Answer 5

If it changes direction without stopping, this means it will be x/0 which is infinity

• changing direction changes acceleration !.

Question 6

HOW TO DESCRIBE Motion if an object on velocity time graph

Answer 6

Say whatever acceleration it si constant whatever

ALWAYS MENTION THE MOMENTARILY STATIONARY POINT
and then what happens after to

Question 7

What is uniform acceleration and what can you do with that

Answer 7

Uniform acceleration is when a body changes its speed at a constant rate , while tracking in a STRAIGHT LINE

If not then it is variable and you can’t use DYNAMICS EQUATIONS WITH THEM

Question 8

How to find acceleration if dynamic

Answer 8

Instsneous gradient

Question 9

Little tricks and things for suvat

Answer 9

Remember that up is negative if getting slower down is positive whatever you lick you keep the same

If it says work out time if flight either do from when it satwitonsrynin air and multiply by two or remember the final velocity is - initial velocity so it becomes. -2 initial velocity basically

Question 10

Remember what’s the acceleration for anything suspended in air (and what about if travelling from trampoline )

Answer 10

Always 9.81, the moment you’ve left trampoline resultant force is 0 and only affecting is gravity and so only gravity is acting when in air

Question 11

What is stopping distance m thninking disrance and breaking distance

Answer 11

Stopping = thinking and breaking

Thinking distance is the distance travelled whilst reacting to having to stop = reaction time x speed and so is dependent on your reaction time and highest speed

Breaking distance is the distance travelled from moment breaks have been applied

Question 12

What factors affect these and how to calculate

Answer 12

Thinking = reaction time and starter speed

Breaking = how good you’re breaks are, how good grip is on Tyree, icy road etc
You calaukte thid using SUVAT, as you are decelerating here

Question 13

What is free fall

Answer 13

The action if a body accelerating solely due to gravity without a DRAG PRODUCING DEVICE

A=g

Question 14

When do we ignore drag and when do we not

(2) situations when we don’t

Answer 14

• ignore if more than 3 orders of magnitude lower
• don’t ignore if BODY MASS is very small compared to surface area (essentially d/m ratio) like a feather
• or you are falling at a very high speed because d is proportional to v2

Question 15

How to do experiment to calculate G PAG METHOD TICKER TAPE

Answer 15

1) Attach a tapper to a pong sheet of paper set at a sertain frequency , and then attach weights to the paper
2) let go , and count the number of dots that appear
3)multiply the number of dots by 1/f , and this gives you the time
4) measure the distance the dots went and this guved you s
Now use s = UT + 1/2AT2 to find A

Question 16

How to find G using electormagnetic method? Trapdoor etc

Answer 16

1) a ball is attached to electromagnet dudpenedover a trapdoor. When current is turned off the magnet demagnetises so ball can drop and a timer is started
2) once the ball hits the trapdoor, electric contact is broken and thus the timer stops

Now can sue value for time, s as height and u to be 0 to find a

Question 17

What are inaccuracies with the electric trapdoor experiment and how can you fix them

Answer 17

So

• time it takes for it to demagnetise is a slight delay from when the timer starts
• also air resistance causes a delay

To improvement

• use a heavier ball = less air resistance?
• and a LONGER DISTANCE so time error uncertainty don’t make much difference

Question 18

How else can you reduce these uncertainties, what equipment

Answer 18

LIGHT GATES! And here detector starts and stops very accurately for the timer

Question 19

How to do the taking pictures method

How to do this using a graph ?

Answer 19

Twke rapid pictures of a ball drilling nedr to ruler

Find values for how far it travelled and how long

Plot a graph of s against t2 due to formula

The gradient is = to 1/2g so multiply by 2

Question 20

With air resistance when is the only time g is 9.81

Answer 20

At t=0 after thst the resultant force decreases and acceleration thus too

Question 21

How to find final velocity basically

Answer 21

Find the time in one plane

Put it in other to find final velocity l
Basically if you have of both now use PYTHAGOREAN remember that’s always how you get it

Question 22

REMEMBER AGAIN TI FALACUKRE FINAK VELOCITY HERE WHAT DO TOU NEED”

Answer 22

Pythagorean and then ANGLE AS IT IS A VECTOR

Question 23

Remember you can do half time hack using when v= 0 as it stops in the sky

Answer 23

So basically make v is 0 when it momentarily stops, due to symmetry time will be double this so x2

Question 24

Remember for projectile motion , if two objects have ONE COMPONENT THE SAME , will they land at the ground at the same time ?

WHAT CHANGES THEN!

Answer 24

YES, the thing linked between components is the time, so if both have one component the same then the time will be the same too!

What changes between components is FINAL SPEED and angle, as speed determined by mangintudes of sperrte velocities !