Question

A toy gun with a spring which is compressed by 3cm is used to project a stone of mass 50g to a height of 10m
a.What is the potential energy of spring?
b.How much it should be compressed to throw the stone to a height?

Answer 1

To reach the peak of 10m the energy of spring must be

Mass = 50g = 50/1000kg = 0.05kg

acceleration due to gravity = g m/s^2 (take it as 10m/s^2 or 9.8 m/s^2 as directed in question)

Height = 10m

P = mgh

 = 0.05 X g X 10 J

= 0.5g J

a) The potential energy of spring to throw it to height 10m is = 0.5g J

Taking g = 10; its 5j

b) To throw obhect to any height 'H' :

Let force coefficent of spring be = k

k X 0.03 = 5

k = 500/3

To throw it to any height H; compression c should be :

k( c) = mgH

500/3 X c = 0.05 X 10 X H

c = 0.05 X 10 X H X 3/500

Substitute the value of any H, to find out c (how much it needs to be compresssed. c is in metres.

All units used are SI units in answer