Post by: 98.40_for_sure on July 01, 2010, 11:23:40 pm
the question has i) and ii)
i) is answer in km/hr^2 (the answer is 12960)
ii) same but express in m/s^2 (stuck!!)
thanks for any help
Post by: Whatlol on July 01, 2010, 11:25:41 pm
anyone got a spare 10 seconds to explain this supposedly easy as question to me :D
the question has i) and ii)
i) is answer in km/hr^2 (the answer is 12960)
ii) same but express in m/s^2 (stuck!!)
thanks for any help
what you converting into km/hr^2 tho...
Post by: 98.40_for_sure on July 01, 2010, 11:28:42 pm
where they give you U(km/hr) V(km/hr) T(sec)
so to find out km/hr^2 i used V = U + AT but first i converted T into hr by x360
i dunno how to explain it... ill just type the question out
A car accelerates uniformly from 5 km/hr to 41 km/hr in 10 seconds. Express the acceleration in i) km/hr^2 ii) m/s^2
Post by: Edmund on July 01, 2010, 11:31:52 pm
Therefore 1s = 1.389m i.e. 1.389m/s
Post by: 98.40_for_sure on July 01, 2010, 11:34:12 pm
i have no idea how you go from 12960 km/hr^2 to 1m/s^2
the worked solution just says x(1/12960)
Post by: Edmund on July 01, 2010, 11:39:08 pm
(11.4-1.4)/10s = 1m/s^2
Post by: Whatlol on July 01, 2010, 11:40:12 pm
the answer surprisingly is... 1m/s^2Im not sure how they did that but i know how to do it another way.
i have no idea how you go from 12960 km/hr^2 to 1m/s^2
the worked solution just says x(1/12960)
simply convert 5km/h into m/s which will become 1.38m/s now do same for 41km/h which will become 11.38m/s
now acceleration is equal to change in velocity over time so 11.38-1.38 =10 and then devide that by 10 which is 10/10 = 1m/s^2
Post by: shinny on July 01, 2010, 11:41:01 pm
Post by: 98.40_for_sure on July 01, 2010, 11:42:49 pm
i did the same but i forgot to square it
i did 12960000/60^2 m/s^2
thank you guys!
Post by: jimmy999 on July 02, 2010, 09:27:56 pm
Start off with something in
If we wanted to convert from km to m, we use unity brackets to multiply the units by effectively 1. We notice that there are 1000m in 1km. Hence we write it as;
This eliminates the km unit. We know that there are 3600s into 1 hour so we can write
Hence
Sometimes though you'll get confused on which part of the fraction to put which unit. Basically if the unit you want to eliminate, such as km is on the top, then first write 1km on the bottom, then 1000m on the top. It will be very useful in other problems you do so you get less confused and make less mistakes
Post by: fady_22 on July 02, 2010, 09:44:40 pm
Post by: /0 on July 02, 2010, 09:55:54 pm
I just use this for conversion between kmh-1 and ms-1: to get from ms-1 to kmh-1, multiply by 3.6. To get from kmh-1 to ms-1, divide by 3.6. Easy. :)
This. And if you can't remember whether to multiply or divide, note that the value in km/h is always greater than the value in m/s.
Post by: 98.40_for_sure on July 02, 2010, 10:28:00 pm
Post by: madoscar65 on August 23, 2010, 10:16:37 pm
Post by: Hutchoo on August 23, 2010, 10:25:35 pm
yeah, x3.6 or devide 3.6.I just use this for conversion between kmh-1 and ms-1: to get from ms-1 to kmh-1, multiply by 3.6. To get from kmh-1 to ms-1, divide by 3.6. Easy. :)
This. And if you can't remember whether to multiply or divide, note that the value in km/h is always greater than the value in m/s.
:P
Post by: m@tty on August 23, 2010, 10:39:58 pm
yeah, x3.6 or devide 3.6.I just use this for conversion between kmh-1 and ms-1: to get from ms-1 to kmh-1, multiply by 3.6. To get from kmh-1 to ms-1, divide by 3.6. Easy. :)
This. And if you can't remember whether to multiply or divide, note that the value in km/h is always greater than the value in m/s.
:P
divide? ...
:P
Post by: Hutchoo on August 23, 2010, 10:41:08 pm