# Determine its speed immediately before landing

## Homework Statement

Please could someone check if I have got this right? Many thanks

The question: An object of mass of 1000kg leaves a 64m high cliff at 100 ms-1 before descending to the ground. Ignoring air resistance, determine its speed immediately before landing.

## Homework Equations

I think its a projectiles question using the 'suvat' equations.

## The Attempt at a Solution

If I'm ignoring air resistance then I assume that mass is irrelevant?

Vertically I have:

u = 0m/s
v = ?
a = 10m/s2
s = 64m
t = ?

Horizontally I have:

u = 100m/s
v = 100 m/s
a = 0m/s2
s = ?
t = ?

Using the vertical components:

s = ut + 1/2 at^2
so
64 = 0 + 1/2 x 10 x t^2
so
t^2 = (2x64)/10 = 12.8s
t = 3.6s

Then

v = u + at
= 0 + (10x3.6)
= 36m/s

That gives me a horizontal velocity of 100m/s and a vertical velocity of 36m/s which using vector addition (Pythagoras) gives an answer of 106.3m/s.

If someone could tell me if I've got that right that would be great, many thanks!