The position function x(t) of a particle moving along an x axis is 
a) The point at which particle stop, it's velocity = 0 m/s
So dx/dt = 0
0 = 0- 12t = -12t
So when time t= 0, velocity = 0 m/s
So the particle is starting from rest.
At t = 0 the particle is (momentarily) stop
b) When t = 0

SO at x = 4m the particle is (momentarily) stop
c) We have 
At origin x = 0
Substituting

t = 0.816 seconds or t = - 0.816 seconds
So when t = 0.816 seconds and t = - 0.816 seconds, particle pass through the origin.
It is definitely letter D. <span>A1 and B1 are like poles, but there is not enough information to tell whether they are north poles or south poles.
A1 and B1 is either both north poles or both south poles. Repulsion of both magnets says it all--like poles always repel while opposite poles always attract. Thus, the best conclusion to this would be choice D.</span>
3 trams must be added
Explanation:
In this problem, there are 12 trams along the ring road, spaced at regular intervals.
Calling L the length of the ring road, this means that the space between two consecutive trams is
(1)
In this problem, we want to add n trams such that the interval between the trams will decrease by 1/5; therefore the distance will become

And the number of trams will become

So eq.(1) will become
(2)
And substituting eq.(1) into eq.(2), we find:

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Answer:
60words/minute
Explanation:
If Sunitha can type 1800 words in half an hour, this can be expressed as;
1800 words = 30 minutes
To get her typing speed per minute, we will use the formula
Speed = Number of words/Time used
Typing speed = 1800/30
Typing speed = 60words/minute
Hence her typing speed in words per minute is 60words/minute
Answer:
D
Explanation:
Speed = distance / time
her time for the first journey = 20 miles / 60 miles/hr = 1/3 hr
her time for second part of the journey = her remaining distance / her speed = (80 - 20) miles / 30 miles/hr = 60 miles / 30 miles/hr = 2 hrs
total time spend by her = 2 hr+ 1/3 hr = 2 1/3 hrs
her traveling the distance at 40 miles per hour = 80 miles / 40 miles /hr = 2 hrs
the time less she would drive if she drive the entire distance at 40 miles/hr = 2 1/3 hrs - 2 hrs = 1/3 hr