bumblebee123
Junior Member
- Joined
- Jan 3, 2018
- Messages
- 200
I've been trying to figure this question out for a while, but I just can't get the right answer. Can anyone help?
Question: a pebble is dropped from the edge of a cliff. The edge of the cliff is 250 metres above the sea. After t seconds, the pebble has fallen a distance of x metres.
x is directly proportional to t^2
when t = 2, x = 19.6
a) find an equation connecting x and t: I managed to do this, the answer was x = 4.9 t^2
b) find the value of x when t = 5: I found this to be 122.5, which was also correct
c) find out how long the pebble takes to fall the final 73.6m before landing in the sea
This is where I get stuck. Here's what I've been doing: 73.6 = 4.9 t^2
15.02.... = t^2
t = sqrt 15.02....
t = 3.875617133
The answer is 1 1/7 seconds
can anyone explain where I'm going wrong? any help would be really appreciated
Question: a pebble is dropped from the edge of a cliff. The edge of the cliff is 250 metres above the sea. After t seconds, the pebble has fallen a distance of x metres.
x is directly proportional to t^2
when t = 2, x = 19.6
a) find an equation connecting x and t: I managed to do this, the answer was x = 4.9 t^2
b) find the value of x when t = 5: I found this to be 122.5, which was also correct
c) find out how long the pebble takes to fall the final 73.6m before landing in the sea
This is where I get stuck. Here's what I've been doing: 73.6 = 4.9 t^2
15.02.... = t^2
t = sqrt 15.02....
t = 3.875617133
The answer is 1 1/7 seconds
can anyone explain where I'm going wrong? any help would be really appreciated