1. ## Kinetic energy/velocity/speed

A 400g lemming waddles horizontally off a small 4.9m high cliff with a horizontal velocity of 0.5m/s.
a) How far from the base of the cliff will the lemming land?
b) What will be the lemming's speed just before landing?
c) What is the lemming's kinetic energy just before landing?

Any help would be appreciated?

Thanks

2. ## Re: Kinetic energy/velocity/speed

Originally Posted by Mr Rayon
A 400g lemming waddles horizontally off a small 4.9m high cliff with a horizontal velocity of 0.5m/s.
a) How far from the base of the cliff will the lemming land?
You should find the time of the free fall (assuming, of course, that the lemming is spherical and in a vacuum). To do this, consider the horizontal and vertical components of the velocity independently and note that the distance traveled from rest in time $\displaystyle t$ with acceleration $\displaystyle g$ is $\displaystyle gt^2/2$. Then multiply this time by the horizontal velocity.

Originally Posted by Mr Rayon
b) What will be the lemming's speed just before landing?
This can be found either by finding the horizontal and vertical components of the landing velocity and using the Pythagoras theorem, or from the law of the conservation of energy. You know the initial energy, which is the sum of the kinetic energy of the horizontal motion and the potential energy due to being on the cliff. At the moment of landing, the lemming has only the kinetic energy, from where the speed can be found.