past questions (1 Viewer)

[doiyoubi]

Ron puts $500 savings into a bank for 2 years, where it earned interest at 6% p.a paid twice a year. He then changed to a Credit Union and his money earned 8% p.a paid quartetly. If he withdrew all his savings and had $633.75, how long was the money kept in the Credit Union?

A boy throws a ball veritcally and it just reaches a height of 40 metres. What is the greatest distance that he is able to throw it on a horizontal plane (g=10ms^-2)

Any help would be great

 

[Riviet]

A boy throws a ball veritcally and it just reaches a height of 40 metres. What is the greatest distance that he is able to throw it on a horizontal plane (g=10ms^-2)

Let u be the initial velocity thrown vertically upwards.
Start with vertical acceleration = -10
Then vertical velocity = -10t + u by integration.
Then vertical displacement = -5t² + ut by integration.
Max height reached when vertical velocity is zero:
0=-10t+u
t=u/10
When vertical displacement = 40 (max height),
40=-5(u/10)² + u²/10
Solving this gives u=20.
Max distance that can be reached is when @=45 where @ is the angle of projection. Derive the range formula and substitute v=20 and @=45.
Hope that helps.

 

[followme]

Q1) 1.5yr?

 

[doiyoubi]

Yep, how did you do it? Thanks

I.ve got some more questions, and ive attached the past paper as well. I'm having trouble with 6b (iii), I think I'm a suppose to find an equation that is independant of veolcity but I cant, and question 7a (i)

thanks

 

[ianc]

Question 6b iii)

Question 7a i)

 

[followme]

at the end of 2nd year, the balance is 500x1.03^4. let that equal to M. M is reinvested into the credit union. so Mx1.02^n=633.75
solve for n and u should get n=5.999 , ie approx. 6 times. Since the interest is paid quarterly, divide 6 by 4 = 1.5