A sweet is modelled as a sphere of radius 10mm and is sucked. After five minutes, the radius has decreased to 7mm. The rate of decrease of the radius is inversely proportional to the square of the radius. How long does it take for the sweet to dissolve?
dr/dt propto -1/r^2 and integrate to find equation linking radius and time with boundary conditions. Set r = 0, answer is 7mins 37 seconds.
IS
Related Maths A Level answers
All answers ▸How do I identify that the coordinate (2,3) is the maximum point of the curve f(x)?
Matthew gets £100 for his 16th birthday and chooses to invest the money into a bank with a 2% annual interest rate. By which birthday will Matthew have more than £150 in his account?
Let f(x)=xln(x)-x. Find f'(x). Hence or otherwise, evaluate the integral of ln(x^3) between 1 and e.
Solve the simultaneous equations, 2x+y-5=0 and x^2-y^2=3