Help with M1 Suvat Equations

Hi. I just started M1 today and we're doing Kinematics. We started with the suvat equations and I'm having trouble with one type of question, where I'm given two of the numbers for suvat, like initial velocity and displacement. An example would be:

'A book of mass 2kg falls from a shelf 150cm above the floor. Find the speed with which the book hits the floor.'

I know s=1.5 and u=0, but I don't know how to go about finding speed when I don't have anything else.

Reply 1

雷尼克

v² = u² + 2as

You know the initial velocity, the acceleration and the displacement - that's enough to calculate the final velocity.

Reply 2

etherealinsanity

Original post by 雷尼克

v² = u² + 2as

You know the initial velocity, the acceleration and the displacement - that's enough to calculate the final velocity.

But I'm not given the acceleration.

Reply 3

雷尼克

Original post by etherealinsanity

But I'm not given the acceleration.

Well acceleration is always the same for a falling object if air resistance is ignored, this is given by the two equations W = mg and F = ma.

Since the weight is the only force acting on an object in most situations in M1, mg = ma.

Therefore the acceleration of a falling object is always a constant, g = a
the value for which is 9.8 ms^-2

Reply 4

etherealinsanity

Original post by 雷尼克

Okay. Thank you very much. I vaguely remember SUVAT equations from Additional maths, but this is the first time I've seen it again in about one and a half years. Thank you again. You've been incredibly helpful. :smile: