# physics

posted by .

Posted by sandhu on Wednesday, November 24, 2010 at 4:29am.

The firetruck goes around a 180°, 162 m radius circular curve. It enters the curve with a speed of 12.6 m/s and leaves the curve with a speed of 38.8 m/s. Assuming the speed changes at a constant rate, what is the magnitude of the total acceleration of the firetruck just after it has entered the curve?

physics - MathMate, Wednesday, November 24, 2010 at 8:16am
From the length of the curve (L=ðr), calculate the average tangential acceleration, At
= (38.8-12.6)/L
Find the radial acceleration due to curvature at entry to curve (v=12.6m/s)
Ar=v²/r
=12.6²/r

Since the two accelerations are perpendicular to each other, add Ar and At vectorially.

physics - sandhu, Wednesday, November 24, 2010 at 7:50pm
I don't understand how you get At = (38.8 - 12.6)/L.Please explain
Thanks.

• physics -

I differ somewhat
I believe that At = change in tangential speed / time. I think he meant t not L
get the time from average speed (38.8+12.6)/2 = 25.7 m/s
now it went pi R = pi(162) = 509 meters
so the time in the turn was
t = 509/25.7 = 19.8 seconds
so I get At = (38.8 -12.6)/19.8
= 1.32 m/s^2

• physics -

Distance is pi(R) but displacement is only 2R ,the diameter of the semi-circle

• physics -

It is the scalar, not the vector, distance we are interested in for the magnitude of the acceleration.

• physics -

Thank you for clarifying

## Similar Questions

1. ### physics

1.A firetruck is traveling at a velocity of +20 m/s in the x direction. As the truck passes x=63m it shoots a tennis ball backwards with a speed of 20 m/s relative to the truck at an angle of 39° from a height of 1.4 m. Neglect air …
2. ### physics

1.A firetruck is traveling at a velocity of +20 m/s in the x direction. As the truck passes x=63m it shoots a tennis ball backwards with a speed of 20 m/s relative to the truck at an angle of 39° from a height of 1.4 m. Neglect air …
3. ### physics

The firetruck goes around a 180°, 162 m radius circular curve. It enters the curve with a speed of 12.6 m/s and leaves the curve with a speed of 38.8 m/s. Assuming the speed changes at a constant rate, what is the magnitude of the …
4. ### physics

Posted by sandhu on Thursday, November 25, 2010 at 6:23am. A block starts with a speed of 18.0 m/s and slides for a distance of 2.2 m down a 40° ramp (ìk = 0.43). What is its final speed?
5. ### physics

Posted by sandhu on Sunday, November 28, 2010 at 10:03pm. A 7200 lb airplane lands on an aircraft carrier with a speed of 72 ft/s. The plane is caught by an elastic band (k=998 lb/ft) that has an initial stretch of 5.6 feet. What is …
6. ### physics

Posted by sandhu on Tuesday, November 30, 2010 at 7:38pm. Posted by sandhu on Tuesday, November 30, 2010 at 1:17am. A T is made of two identical 740 g thin solid rods. The moment of inertia of the T about an axis perpendicular to the …
7. ### College math

Highway curves If a circular curve without any banking has a radius of R feet, the speed limitL.in miles per hour for the curve is L=1.5 R. (a.)Find the speed limit for a curve having a radius of 400 feet. (b.) If the radius of a curve …
8. ### physics

A car going 30 m/s just barely makes it around a curve without skidding. This curve had a radius of 150 m. The next curve has a radius of 75 m. At what maximum velocity can it go around this curve without skidding?
9. ### Physics

A car drives around a curve with radius 150 m at a speed of 30 m/s. What is the average acceleration at?
10. ### Physics

Engineering a highway curve. If a car goes through a curve too fast, the car tends to slide out of the curve. A frictional force acts on a fast car to oppose the tendency to slide out of the curve. Consider a circular curve of radius …

More Similar Questions