Calculating Force of Gravity on an Alien Frog

[get_rekd]

Homework Statement

An alien form of frog with a mass of 1.5kg (on a planet with an unknown acceleration of gravity) jumps up from his lilly pad at a velocity of 4.0m/s. If the frog reaches a maximum height of 15m, what is the force of gravity on the frog on this planet?

It's a stupid question but I am totally stuck on it??

 

[mjsd]

hint: this's a constant acceleration problem

 

[get_rekd]

Sorry I totally missed the days that we went over this in class. I am not sure where to start with a constant acceleration problem?

 

[mjsd]

perhaps first identify what are the equations you have learn about kinematics with constant acceleration.. (can easily google them). then identify what is given in question, and what you what to work out.

 

[slakedlime]

I think you can solve this using the equations of motion and algebra. First find the time using the following equation:

v = u + at

When the frog reaches his maximum height, v = 0 m/s.

Then use the following formula:

s = ut + 0.5a(t^2)

Here s is the vertical height (15m) reached. You'll have to do a bit of substitution from the first formula, since both a and t are unknowns.

I hope that helps. :)