Physics Homework Help 2?

Question

3. The polar bear is an excellent swimmer, and it spends a large part of its time in the water. Suppose a polar bear wants to swim from an iceberg to a place in shore where seals gather. The bear starts swimming at a velocity of 2.60 m/s. By the time it reaches the shore, its velocity has decreased to 2.20 m/s. If the polar bear's swim takes 9 minutes and it has a constant deceleration, what is the distance traveled by the polar bear?

4. A daredevil motorcycle rider pops a wheelie at a velocity of 8 m/s. He finds he needs to speed up to maintain this stuntm and so accelerates at 2 m/s^2 and travels 40 m during this acceleration.
a. What is the rider's velocity after the acceleration?
b. How much time did it take to travel this distance?

Answer 1

Ooh I'm doing problems like this in my Physics Honors class!
I want to help you too not just show you the answers soo here is how I did it:

3) Polar Bear ---------------------------------> Seal
Vi = 2.60 m/s , Vf = 2.20 m/s

You need to find d (distance), so use this formula:

x = 1/2 (vi+vf) t
x = 1/2 (2.60 + 2.20) 9
x = 1/2 (4.8) 9
x = 2.4 (9)
x = 21.6 meters

I don' think my part 4 is right (b) so i don't want to mess you up . :D hope this helps

4) you know... v = 8 m/s , a = 2 m/s^2 , d = 40 m
a) to find velocity after acceleration...
1/2at^2 = x
1/2 2t^2 = 40
t = square root 40 = 6.32 sec
[he accelerates for 6.32 sec] so take 6.32s x 2 m/s because you know Velocity = at
so the answer is 12.64 m/s

Answer 2

Toasted Fart did good work on #3 but I disagree on #4. Gotta remember the initial velocity: Vi=8 m/s.

a. To find the final velocity, use
Vf^2 = Vi^2 + 2*a*d

b. To find the time, use
Vf = Vi + a*t