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/sci/ - Science & Math

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2743043 No.2743043 [Reply] [Original]

Hai guise. Physic student fag here.


got exam on tuesday and just realised today so was doing questions online and after looking at a past one saw this:

A stone S is sliding on ice. The stone is moving along a straight line ABC, where AB = 24 m
and AC = 30 m. The stone is subject to a constant resistance to motion of magnitude 0.3 N.
At A the speed of S is 20 m s–1, and at B the speed of S is 16 m s–1. Calculate

(a) the deceleration of S,
(2)
(b) the speed of S at C.

I literally dont have any idea what to do.

Ive tried using suvat

but im not sure what displacement i use and stuff

any hepl? tnx

>> No.2743049

If you can't handle a basic dynamics problem its time to drop out of physics.

>> No.2743051

I also forgot to add i dont know if im working out acceleration or velocity for (a)

is there an easy way to tell which one you have to work out?

thanks

>> No.2743055

>>2743049
Kinematics is my only problem

if the test was on statics distance time graph or moments i would ace it also its just this part of dynamics i dont understand i understand everything else such as newtons 2nd law f=ma.


Its just these suvat questions i get everything else.

thanks

>> No.2743064
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2743064

>>mfw i know the answer

>> No.2743067

Ok bump. I now get -3 when the answers meant to be 3 is this normal?

>> No.2743072

what the hell is suvat?

>> No.2743077

>>2743067

-3 represents deceleration of 3ms^-2. so you can it has acceleration of -3 and a deceleration of 3

>> No.2743082

is answer to b) 8.72m/s op?

>> No.2743090

>>2743082
nuh 14.8

>> No.2743099

>>2743090

oh yh i derped hard. i made BC = 30m when it should have been 6m

>> No.2743113

>>2743072
>The equations that apply to bodies moving linearly (in one dimension) with constant acceleration are often referred to as "SUVAT" equations where the five variables are represented by those letters (s = displacement, u = initial velocity, v = final velocity, a = acceleration, t = time); the five letters may be shown in a different order.
http://en.wikipedia.org/wiki/Equations_of_motion

>> No.2743128

i havent even read the question, but that looks so easy.

>> No.2743136
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2743136

>>2743072
no idea

>> No.2743239

At C, the stone S hits a vertical wall, rebounds from the wall and then slides back along the
line CA. The magnitude of the impulse of the wall on S is 2.4 N s and the stone continues to
move against a constant resistance of 0.3 N.
(d) Calculate the time between the instant that S rebounds from the wall and the instant that S
comes to rest.

can anyone help me with this?