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Acceleration - Physics?
I need help with these problems. You necessary don't have to do them, just give me hints on how to get to the right answers. I do want to learn and solve similar problems to these problems!
A plane accelerates from rest at 20 m/s^2 down a runway. If its takeoff speed must be 80 m/s, how long will it take (in seconds) to reach max speed?
A jet aircraft being launched from an aircraft carrier is accelerated from rest along a 94 m platform for 2.5 seconds. What is the launch speed in m/s?
The driver of a truck going 100 km/hr applies the brakes, accelerating at -6.5 m/s^2. How many seconds does it take to stop?
1 Answer
- JullyWumLv 79 years agoFavorite Answer
1) a = 20m/s², initial vel u = 0, final vel v = 80m/s
• v = u + at ..rearrange .. ►t = (v - u) / a
2) u = 0, d = 94m, t = 2.5s .. .. find final speed v
• Average vel = d/t .. gives .. ½(u + v) = d/t
as u = 0 .. ½v = d/t .. .. rearrange .. ►v = 2dt
3) u = 100km/h = 100,000m / 3600s .. initial vel u = 27.78 m/s
a = -6.5 m/s², final vel v = 0
• v= u + at
rearrange .. t = (v-u)/a .. both (v-u) and (a) are negative, leaving t +ve
