Date | November 2015 | Marks available | 2 | Reference code | 15N.2.hl.TZ0.9 |
Level | HL only | Paper | 2 | Time zone | TZ0 |
Command term | Find | Question number | 9 | Adapted from | N/A |
Question
A particle can move along a straight line from a point O. The velocity v, in ms−1, is given by the function v(t)=1−e−sint2 where time t≥0 is measured in seconds.
Write down the first two times t1, t2>0, when the particle changes direction.
(i) Find the time t<t2 when the particle has a maximum velocity.
(ii) Find the time t<t2 when the particle has a minimum velocity.
Find the distance travelled by the particle between times t=t1 and t=t2.
Markscheme
t1=1.77 (s)(=√π (s))andt2=2.51 (s)(=√2π (s)) A1A1
[2 marks]
(i) attempting to find (graphically or analytically) the first tmax (M1)
t = 1.25{\text{ (s)}}\;\;\;\left( { = \sqrt {\frac{\pi }{2}} {\text{ (s)}}} \right) A1
(ii) attempting to find (graphically or analytically) the first {t_{\min }} (M1)
t = 2.17{\text{ (s)}}\;\;\;\left( { = \sqrt {\frac{{3\pi }}{2}} {\text{ (s)}}} \right) A1
[4 marks]
distance travelled = \left| {\int_{1.772 \ldots }^{2.506 \ldots } {1 - {{\text{e}}^{ - \sin {t^2}}}{\text{d}}t} } \right|\;\;\;(or equivalent) (M1)
= 0.711{\text{ (m)}} A1
Note: Award M1 for attempting to form a definite integral involving 1 - {{\text{e}}^{ - \sin {t^2}}}. To award the A1, correct limits leading to 0.711 must include the use of absolute value or a statement such as “distance must be positive”.
In part (c), award A1FT for a candidate working in degree mode \left( {5.39{\text{ (m)}}} \right).
[2 marks]
Total [8 marks]