Question

I can't understand this problem :(

Answer 1

https://goo.gl/photos/QEtDoH1SFKowyFk9A

Answer 2

dont cry eat a Snickers and ask jimmy

Answer 3

@jim_thompson5910

Answer 4

:) ty

Answer 5

pleasure is mine

Answer 6

I'm not sure. I'm not that great with physics but let me do a bit of searching.

Answer 7

Oh ok :)

Answer 8

is there any way you could type this out to make the searching easier

Answer 9

I think this problem has to do with f=ma newtons 2nd law of motion

Answer 10

Maybe solving for f but I don't know a thougb

Answer 11

Im on my phone lol i can't really type

Answer 12

I am pretty sure this is an impulse momentum question. Thinking and reading.

Answer 13

Brb

Answer 14

@Fanduekisses

Answer 15

Hi

Answer 16

Why doesn't anyone draw diagrams!

Answer 17

Notice that the skateboard took 30s to stop the skateboarder who was travelling at a speed of 15 m/s.

Initial velocity = 15 m/s
Final velocity = 0 m/s
Time taken = 30s

Based on above 3 pieces of given info, can you find the acceleration ?

Answer 18

Sorry that I'm late lol but yeah I can find the acceleration since it's just change in velocity over time. :)
\[a(t)=\frac{ 1 }{ 2 }m/s^2\]

Answer 19

(-) minus

Answer 20

So I look at the forces acting on the skateboard, add them together and set them equal to m*a and solve for that force applied? I'm starting to get this sort of hehe

Answer 21

You need to consider only one force here. The force from skateboard that has decelerated the skateboarder

Answer 22

\[F_{skatebord}=70*-.5\]

Answer 23

Looks good

Answer 24

is this question still open for a physics party?

Answer 25

diagram for sensei @astrophysics

Answer 26

@nincompoop very nice

Answer 27

@nincompoop how about drawing a FBD :3

Answer 28

Althought the question says the 'weight ' is 70 kg it is not using the term correctly

The MASS of th eperson is 70 kg

@nincompoop
Your diagram should show "mg" as the weight. However the weight acting vertically down is not relevant to this questions, as the acceleration is horizontal.

@Fanduekisses
Your hand notes on the question show that oyu already have the answer.

As noted above the acceleration is -0.5m/s^2
and you have written on the page (F) = ma = 70*-.5 = -35N

The minus just means the force acts in th opposite direction to the motion.

Answer 29

By the way
For a physics question to confuse mass and weight is unforgiveable in my opinion!

If your teacher set this (rather than online) I would raise that issue with him/her

Answer 30

no one is confusing weight and mass here
w = mg

Answer 31

you have indicated that the force w = 70 kg

kg is a measure of MASS

the weight acting down is 70kg * 9.81 m/s^2 = 687 NEWTONS

Newtons is the unit of FORCE or weight

You have confused mass with weight - and so has the question

Answer 32

I missed class that day and I got those notes from a class mate.

Answer 33

Thanks guys!

Answer 34

Clarification:
the mass of the person is the amount the person weighs measured in kg.
force is the mass times the acceleration measured in newtons.

the possible misunderstanding is in the question the person WEIGHTS

Answer 35

@triciaal That is not a clarification

Mass is NOT what a person weighs "in kg"

A mass and weight are entirely different physical entities.

The mass of an object is a measure of how much of the object is present, and is constant if the object doesn't change physically

In classical physics the Weight is the force that an object exerts when acted upon by the acceleration of gravity

Weight is a FORCE, mass is NOT.

If you look at the dimension of the entities
Mass has Dimensions "Mass"
Force and hence weight has dimension "Mass * Distance * Time^-2"

A body has the same mass on earth, mars, space, or wherever but the WEIGHT is dependent on the gravitational field in which it is measured.

I am not sorry to keep on about this -it is a FUNDAMENTAL concept in physics and anyone using mass and weight interchangeably has not got a clear understanding of the physics.

"Lecture over (for now)"