![](../../image/prcpywrt.gif)
A bicycle coasts down a steep, 80 meter tall, hill. Neglecting air
friction, how fast will it be going when it gets to the bottom?
(A) 12m/s.
(B) 28m/s.
(C) 40m/s.
(D)1600m/s
![](../../image/prcpywrt.gif)
A bicycle coasts down a steep, 80 meter tall, hill. Neglecting air
friction, how fast will it be going when it gets to the bottom?
(A) 12m/s. --- No.
P.E. = mgh. Don't forget g=10m/s
![](../../image/prcpywrt.gif)
A bicycle coasts down a steep, 80 meter tall, hill. Neglecting air
friction, how fast will it be going when it gets to the bottom?
(B) 28m/s. --- No.
K.E. = (1/2)mv
. Don't forget the 1/2.
![](../../image/prcpywrt.gif)
A bicycle coasts down a steep, 80 meter tall, hill. Neglecting air
friction, how fast will it be going when it gets to the bottom?
(C) 40m/s --- Yes.
(1/2)mv
= mgh:
v
= 2gh = (2)(10)(80)m
/s
= 1600m
/s
![](../../image/prcpywrt.gif)
A bicycle coasts down a steep, 80 meter tall, hill. Neglecting air
friction, how fast will it be going when it gets to the bottom?
(D) 1600m/s --- No.
K.E. = (1/2)mv
.
Don't forget that v is squared.