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# I need help in these questions in details

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I need help in these questions in details

and Please understand that I struggle a little with English

I determine the velocity is negative because the slope is negative ! I chose (b) .. right ?

physics
Aug 26, 2014

#12
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17) is c.

I think all the others have been answered.

Aug 26, 2014

#1
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+5

length = + 5
time = +2
v= 5/2 = + 2.5

Aug 26, 2014
#2
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the length still bositive any way the direction is nigative or not

Aug 26, 2014
#3
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Question 5 is right.

Question 11   There may be a 'normal' method for doing this, I am not a physics specialist.

$$magnitude\\ =\sqrt{7.6^2+5.2^2}\\ =9.20869\\ =9.2$$

$$\\tan\theta=\frac{5.2}{7.6}$$

$$\underset{\,\,\,\,^{{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{5.2}}}{{\mathtt{7.6}}}}\right)} = {\mathtt{34.380\: \!344\: \!723\: \!845^{\circ}}}$$

direction = 180+34.38 = 214.38 degrees

So the answer is B      9.2 and 214.38 degrees with the positive x axis.

If you do not understand what I have done then make sure you ask me to explain more.

Aug 26, 2014
#4
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Thank you aliammar

Melody .. its very clear .. the mistake that I do un my solution that I took this angle

Aug 26, 2014
#5
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Good,

Lets try question 16

easterly force = 3N

Northerly force =4N

Use Pythagoras's theorem to get net force.

sqrt(9+16)=5N

Now,  F=ma

5=2*a

$$acceleration =5/2=2.5m/s^2$$

.
Aug 26, 2014
#6
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Question 19

NOTE:    I do not know this stuff.  I am referencing this site

http://zonalandeducation.com/mstm/physics/mechanics/forces/newton/mightyFEqMA/mightyFEqMA.html

It looks pretty good.

u=30m/s,  mass=2000kg,  Braking force=10000N,  v=0,   find t

F=ma    therefore a=F/m=-10000/2000=-5m/s2

v=u+at

0=30-5t

5t=30

t=6 seconds

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d=ut+(1/2)at2

d=30*6+(1/2)(-5)*36

d=180+-90

distance=90metres      I think that D is the answer.

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Aug 26, 2014
#7
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for 16 .. Now its very clear  thank you

Aug 26, 2014
#8
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I don't know question 17 sorry.

Aug 26, 2014
#9
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for 19 .... also now its very clear

Aug 26, 2014
#10
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For question 5) the average velocity is (x(4secs) - x(2secs))/(4secs - 2secs)

This is (5 - 10)/(4 - 2) = -5/2 = -2.5 m/s

So b is the correct answer.

Aug 26, 2014
#11
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Thank you alan ... waiting for remaining questions

Aug 26, 2014
#12
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17) is c.

I think all the others have been answered.

Alan Aug 26, 2014
#13
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Thanks Alan.

Aug 27, 2014
#14
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Thanks for all ... alan and melody

Aug 28, 2014