Question
A box accidentally falls from the back of a truck and hits the ground with a speed of 15m/s. It slides along the ground for a distance of 45 m before coming to rest. Determine
a) the length of time the box slides before stopping
c) the time it takes to slide the last 10 m.
a) the length of time the box slides before stopping
c) the time it takes to slide the last 10 m.
Answers
drwls
a) Its average speed while coming to a stop is 7.5 m/s. Divide 45 m by that average speed to get the time required. You get 6.00 s
b)The speed while slowing down is
V = 15 [1 - (t/6)]
The time required to go 35 m is given by
Integral V dt = 35 = 15 t - (5/4)t^2
0 to t
Solve that quadratic for t. That will be the time required to slide the first 35 m. Subtract that from 6 s for the answer.
b)The speed while slowing down is
V = 15 [1 - (t/6)]
The time required to go 35 m is given by
Integral V dt = 35 = 15 t - (5/4)t^2
0 to t
Solve that quadratic for t. That will be the time required to slide the first 35 m. Subtract that from 6 s for the answer.
Alex
Why is the velocity 7.5?
Smartypants
A better solution is using the big 5 equations
yagmur
the area under the velocity versus time graph gives you the total displacement so;
30.t/2 = 45
t= 30
30.t/2 = 45
t= 30