Problem 1
A car starts from rest at time t = 0 and accelerates at -0.6t + 4 meters/sec^{2} for 0<t<12. How long does it take for the car to go 100 meters?
here is my work:
Problem 2
A 727 jet needs to attain a speed of 200 mph to take off. If it can accelerate from 0 to 200 mph in 30 seconds, how long must the runway be? (Assume constant acceleration and give your final answer in feet)
here is my work:
200 miles per hour = ft/sec
ft/sec divided by 30 sec = ft/sec
ft/sec
ft/sec
ft/sec
ft.
Please check the conversions and overall answer.
Problem 3
On the moon, the acceleration due to gravity is about 1.6 m/sec (compared to m/sec on earth). If you drop a rock on the moon (with initial velocity 0), find formulas for:
(a) Its velocity, v(t), at time t.
(b) The distance, s(t), it falls in time t.
here is my work:
m/sec
m/sec
(a) m/sec
(b) , where K is the initial height.
Should I keep the constant K in this answer? and how about the constants in all the other problems? I'm confused whether I need them or not.. In the previous ones I assumed the initial values were 0. Can I do this?
Look at what he wrote he
tell you that , which leaves you with:
To find how long it takes to go 100 metres you set in the above equation and solve for . Which gives you the
following cubic to solve:
,
which the observant will note has a root at , and the other roota are either negative ( and so irrelevant) or at a time greater than 12 (and so also irrelevant).
So it takes 10 seconds for the car to go 100 metres.
RonL