Kinematics Help

[OnlyThorns]

Ok. So I don't get them at all. I have a MAJOR test on Monday, not to mention some homework grades. I have been able to do some of the problems, but the following are stumping me. If anyone knows the answers that would be great. What would be better is if you could tell me how to do it. Thanks!

 

 

3) The length of the barrel of a primitive blowgun is 1.2 m. Upon leaving the barrel, a dart has a speed of 11 m/s. Assuming that the dart is uniformly accelerated, how long does it take for the dart to travel the length of the barrel?

 

4) (a) What is the magnitude of the average acceleration of a skier who, starting from rest, reaches a speed of 6.8 m/s when going down a slope for 4.8 s?

(b) How far does the skier travel in this time?

 

5) A runner accelerates to a velocity of 5.37 m/s due west in 3 s. His average acceleration is 0.641 m/s2, also directed due west. What was his velocity when he began accelerating?

 

6) NASA has developed Deep-Space 1 (DS-1), a spacecraft that is scheduled to rendezvous with the asteroid named 1992 KD (which orbits the sun millions of miles from the earth). The propulsion system of DS-1 works by ejecting high-speed argon ions out the rear of the engine. The engine slowly increases the velocity of DS-1 by about 19.0 m/s per day.

(a) How much time (in days) will it take to increase the velocity of DS-1 by 11900 m/s?

(b) What is the acceleration of DS-1 (in m/s2)?

 

7) A tourist being chased by an angry bear is running in a straight line toward his car at a speed of 3.9 m/s. The car is a distance d away. The bear is 28 m behind the tourist and running at 6.0 m/s. The tourist reaches the car safely. What is the maximum possible value for d?

 

 

Thanks again. I am not very good at physics.

[ydoaPs]

Ok. So I don't get them at all. I have a MAJOR test on Monday' date=' not to mention some homework grades. I have been able to do some of the problems, but the following are stumping me. If anyone knows the answers that would be great. What would be better is if you could tell me how to do it. Thanks!

 

1) As the earth rotates through one revolution, a person standing on the equator traces out a circular path whose radius is equal to the radius of the earth (6.38 106 m). What is the average speed of this person in meters per second and miles per hour? [/quote']use the radius to find the circumference. divide the circumference by 1 day. then use factor label to get your answer in the desired units.

2) A car is traveling at a constant speed of 16 m/s on a highway. At the instant this car passes an entrance ramp, a second car enters the highway from the ramp. The second car starts from rest and has a constant acceleration. What acceleration must it maintain, so that the two cars meet for the first time at the next exit, which is 2.2 km away?

[math]x=x_0+v_0t+\frac{1}{2}at^2[/math]. you will need to use it more than once. find the time it takes for the first car to go 2.2km and then use that time to find a.

3) The length of the barrel of a primitive blowgun is 1.2 m. Upon leaving the barrel, a dart has a speed of 11 m/s. Assuming that the dart is uniformly accelerated, how long does it take for the dart to travel the length of the barrel?

[math]v^2=v_0^2+2a{\Delta}x[/math]

4) (a) What is the magnitude of the average acceleration of a skier who, starting from rest, reaches a speed of 6.8 m/s when going down a slope for 4.8 s?

(b) How far does the skier travel in this time?

a=v/t and use the distance formula from above.

5) A runner accelerates to a velocity of 5.37 m/s due west in 3 s. His average acceleration is 0.641 m/s2, also directed due west. What was his velocity when he began accelerating?

[math]v^2=v_0^2+2at[/math]

6) NASA has developed Deep-Space 1 (DS-1), a spacecraft that is scheduled to rendezvous with the asteroid named 1992 KD (which orbits the sun millions of miles from the earth). The propulsion system of DS-1 works by ejecting high-speed argon ions out the rear of the engine. The engine slowly increases the velocity of DS-1 by about 19.0 m/s per day.

(a) How much time (in days) will it take to increase the velocity of DS-1 by 11900 m/s?

(b) What is the acceleration of DS-1 (in m/s2)?

old physics text?

since you only need to know how much it increases, you can set initial velocity to 0 and use [math]v^2=v_0^2+2at[/math] for a, use the 19.0m/s/day and use factor label

7) A tourist being chased by an angry bear is running in a straight line toward his car at a speed of 3.9 m/s. The car is a distance d away. The bear is 28 m behind the tourist and running at 6.0 m/s. The tourist reaches the car safely. What is the maximum possible value for d?

i'll have to think about this one. i'll answer back in a bit

[ydoaPs]

some may not know what factor label is. it is simply converting units my way of multiplying fractions so that units cancel leaving only the desired units.

 

say you want to go from 7cal into J. [math]\frac{7cal}{1}*\frac{4.184J}{cal}{\to}30J[/math]

 

2miles/hr to m/s [math](\frac{2mi}{hr})(\frac{hr}{3600s})(\frac{1609m}{mi}){\to}.9m/s[/math]

 

note:i suck at significant digits, so i just rounded however i wanted

[OnlyThorns]

ok i have 29801.4 meters per hour and I need to conver that to miles per hour. i know that 1 mile is 1609 meters. so i take 29801.4meters/1609meters

 

the meters cancel out. leaving me with 18.5 miles per hour...

but it says i have this wrong.

 

[[math]] 29801.4m/1609m = 18.5 [[/math]]

[ydoaPs]

take [math]|\frac{2{\pi}(6.38x10^6)m}{day}|\frac{day}{24hr}|{\frac{hr}{3600s}}|[/math] the hours cancel leaving you with m/s.

 

let x=previous answer and take [math]|\frac{xm}{s}|\frac{mi}{1609m}|\frac{3600s}{hr}|[/math] the seconds and meters cancel leaving mi/hr.

 

it's all about the factor label

[OnlyThorns]

7) A tourist being chased by an angry bear is running in a straight line toward his car at a speed of 3.9 m/s. The car is a distance d away. The bear is 28 m behind the tourist and running at 6.0 m/s. The tourist reaches the car safely. What is the maximum possible value for d?

[swansont]

7) A tourist being chased by an angry bear is running in a straight line toward his car at a speed of 3.9 m/s. The car is a distance d away. The bear is 28 m behind the tourist and running at 6.0 m/s. The tourist reaches the car safely. What is the maximum possible value for d?

 

Assuming no time to open the door and get in, the time for you and the bear to cover their respective distances will be the same. d=vt

[ydoaPs]

when doing physics, remember that it isn't just putting in numbers into a formula. it is about problem solving. sometimes you just have to think about the problem. keep at it. Arbeit macht frei!

[ydoaPs]

here's a hard one. it took me a few minutes. try it.

 

 

A basketball leaves a player's hands at a height of 2.10m above the floor. The basket is 2.60m above the floor. The player likes to shoot the ball at 38.0 degree angle. If the shot is made from a horixontal distance of 11.00m and must be accurate to plus or minus 0.22m (horizontally), what is the range of initial speeds allowed to make the basket?

[OnlyThorns]

Hey. If you ever need help...ask yourdad. He is really helpful and sweet. If I had to give him a kiss for all that he has helped me with, he'd be smothered.

*big kiss*

Thanks soooo much. I'll try your problem later I want to relax for a while.......

~onlythorns

[ydoaPs]

here's an easy question if your class adds another dimension. you only need the equations you already have.

 

Given; A=<3,-2,-4>m/s^2 , V₀=<1,2,3>m/s, R₀=<30,-80,40>m, T=8s.

Find; R, V, V_ave

 

[hide]R=<30,-80,40>, v=<25,-14,-29, v_avg=<13,-6,-13>[/hide]