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Date November 2020 Marks available 5 Reference code 20N.1.SL.TZ0.S_7
Level Standard Level Paper Paper 1 (without calculator) Time zone Time zone 0
Command term Find Question number S_7 Adapted from N/A

Question

In this question, all lengths are in metres and time is in seconds.

Consider two particles, P1 and P2, which start to move at the same time.

Particle P1 moves in a straight line such that its displacement from a fixed-point is given by st=10-74t2, for t0.

Find an expression for the velocity of P1 at time t.

[2]
a.

Particle P2 also moves in a straight line. The position of P2 is given by r=-16+t4-3.

The speed of P1 is greater than the speed of P2 when t>q.

Find the value of q.

[5]
b.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

recognizing velocity is derivative of displacement     (M1)

eg    v=dsdt , ddt10-74t2

velocity=-144t   =-72t        A1 N2

[2 marks]

a.

valid approach to find speed of P2     (M1)

eg    4-3 , 42+-32 , velocity=42+-32

correct speed     (A1)

eg   5m s-1

recognizing relationship between speed and velocity (may be seen in inequality/equation)        R1

eg   -72t , speed = | velocity | , graph of P1 speed ,  P1 speed =72t , P2 velocity =-5

correct inequality or equation that compares speed or velocity (accept any variable for q)      A1

eg   -72t>5 , -72q<-5 , 72q>5 , 72q=5

q=107 (seconds) (accept t>107 , do not accept t=107)       A1   N2

 

Note: Do not award the last two A1 marks without the R1.

[5 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 5 —Calculus » SL 5.9—Kinematics problems
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Topic 3— Geometry and trigonometry » AHL 3.14—Vector equation of line
Topic 3— Geometry and trigonometry
Topic 5 —Calculus

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