Date | May 2021 | Marks available | 2 | Reference code | 21M.1.SL.TZ2.9 |
Level | Standard Level | Paper | Paper 1 (without calculator) | Time zone | Time zone 2 |
Command term | Find | Question number | 9 | Adapted from | N/A |
Question
Particle A travels in a straight line such that its displacement, s metres, from a fixed origin after t seconds is given by s(t)=8t-t2, for 0≤t≤10, as shown in the following diagram.
Particle A starts at the origin and passes through the origin again when t=p.
Particle A changes direction when t=q.
The total distance travelled by particle A is given by d.
Find the value of p.
Find the value of q.
Find the displacement of particle A from the origin when t=q.
Find the distance of particle A from the origin when t=10.
Find the value of d.
A second particle, particle B, travels along the same straight line such that its velocity is given by v(t)=14-2t, for t≥0.
When t=k, the distance travelled by particle B is equal to d.
Find the value of k.
Markscheme
setting s(t)=0 (M1)
8t-t2=0
t(8-t)=0
p=8 (accept t=8, (8, 0)) A1
Note: Award A0 if the candidate’s final answer includes additional solutions (such as p=0, 8).
[2 marks]
recognition that when particle changes direction v=0 OR local maximum on graph of s OR vertex of parabola (M1)
q=4 (accept t=4) A1
[2 marks]
substituting their value of q into s(t) OR integrating v(t) from t=0 to t=4 (M1)
displacement=16 (m) A1
[2 marks]
s(10)=-20 OR distance=|s(t)| OR integrating v(t) from t=0 to t=10 (M1)
distance=20 (m) A1
[2 marks]
16 forward + 36 backward OR 16+16+20 OR 10∫0|v(t)|d (M1)
A1
[2 marks]
METHOD 1
graphical method with triangles on graph M1
(A1)
(A1)
A1
METHOD 2
recognition that distance M1
(A1)
(A1)
A1
[4 marks]