Question

(Law of Motion) A force of 300 n slows down a wagon from 40 kph to 20 kph in 10 seconds. What is the wagon's weight?

Answer 1

Use the equation \[\Sigma F = ma\] and solve for m then after you have m you use
\[F_g = mg\] where g = 9.8 N/kg

Answer 2

Would that be the only formula for the problem?

Answer 3

two different equations I am not replace Fg with the top equation

Answer 4

okay thanks :)

Answer 5

let me know if you need more assistance

Answer 6

Could you help me in using ΣF=ma ? I dont know how to solve using this equation

Answer 7

I believe the deceleration should be found first.
using 1 of 3 kinematic equations, find what -acceleration is required to go from 40km/h down to 20km/h in 10 seconds.
If your not sure which equation to use, let me know

Answer 8

\[velocity= \frac{ \Delta displacement }{ time }\] is this correct?

Answer 9

wait.. have you been introduced to these equations?
v^2=v^2 + 2as
v=v+at
s=s+vt+(1/2)at^2

Answer 10

no. :/

Answer 11

they don't look familiar at all? none zip no-way no-how?

Answer 12

they dont look familiar

Answer 13

ok ^_^ no problem
so we will find acceleration using this equation:
acceleration = (velocity_2 - velocity_1)/time

Answer 14

where velocity_2 is 40km/h
velocity_ = 20km/h

Answer 15

when you wrote, " 40 kph to 20 kph" do you mean "40km per hour to 20km per hour"?

Answer 16

yeah :)

Answer 17

ok good :)
so anytime you do use an equation that has to do with velocity. we have to make sure that velociy is meters per second. here you are given kilometers per hour. so you'll need to convert km/h into m/s, can you do this?

Answer 18

yeah. :) so the new one is 11.11 m/s to 5.56 m/s Am I right?

Answer 19

yes, good work ^_^
now we will use those to figure out the negative acceleration that the wagon is experiencing with this:
\[acceleration = \frac{ Velocity_{faster} - Velocity_{slower} }{ time}\]

Answer 20

then the acceleration would be = \[\frac{ 20 m/s }{ 10s }\] ?

Answer 21

then the result would be 2 m? is that an acceleration? or am I worng?

Answer 22

think again..
remember what you got here:
"yeah. :) so the new one is 11.11 m/s to 5.56 m/s Am I right?"
use these numbers, becuase we have to have it in m/s

Answer 23

ooops. i forgot so its \[\frac{ 5.55 m/s }{ 10 s}\]

Answer 24

very good ^_^

Answer 25

thanks :) so what's next?

Answer 26

so finishing out the math, we have
5.55/10 = 0.55
0.55 m/s^2 is the rate at which the wagon is being slowed down (negative acceleration)

Answer 27

now that we know how much it is being slowed down. we can find out it's mass.
this is where we will use the equation:
force = mass*acceration
we know acceleration,
we know force [given in the problem information]
so now we solve for mass ^_^

Answer 28

so, in finding mass, it would be \[\frac{ 300N }{ 0.55 m/s ^{2}}\] then the result would be 545.45 kg

Answer 29

bingo ^_^

Answer 30

Ohhhhhhhhhhhhhhh! Thanks so much :)

Answer 31

your welcome ^_^
i'm logging off now, have a good evening

Answer 32

You too. Thanks again :)