A free Sec 4 A-Math worksheet on kinematics: 5 questions, 40 marks, short questions first and then structured ones, in the school exam style. The answers and full worked solutions are on the last page.
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Answer all questions. Show all your working. Give non-exact answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless the question says otherwise.
Section A
1
(a)A particle moves in a straight line so that, t seconds after passing through a fixed point O, its velocity, v m/s, is given by v=9t2−8t. Find its displacement from O when t=3.
Answer (a)[3]
(b)A particle moves in a straight line so that, t seconds after passing through a fixed point O, its acceleration, a m/s², is given by a=4t+3. Its initial velocity is −3 m/s. Find its velocity when t=2.
Answer (b)[3]
2
(a)A particle moves in a straight line so that, t seconds after passing through a fixed point O, its velocity, v m/s, is given by v=3t2−42t+120. Find the total distance travelled by the particle in the first 9 seconds.
Answer (a)[3]
(b)A particle moves in a straight line so that, t seconds after passing through a fixed point O, its velocity, v m/s, is given by v=t2−8t+12. Find the total distance travelled by the particle in the first 5 seconds.
Answer (b)[3]
3
(a)A particle moves in a straight line so that, t seconds after passing through a fixed point O, its displacement from O, s m, is given by s=t3−12t2+36t. Find its acceleration when t=2.
Answer (a)[3]
(b)A particle moves in a straight line so that, t seconds after passing through a fixed point O, its displacement from O, s m, is given by s=2t3−24t2+42t. Find the values of t at which the particle is instantaneously at rest.
Answer (b)[3]
Section B
4
A particle moves in a straight line so that, t seconds after passing through a fixed point O, its velocity, v m/s, is given by v=12e−2t−2.
(a)Find the initial velocity of the particle.
Answer (a)m/s[1]
(b)Find the initial acceleration of the particle.
Answer (b)m/s²[2]
(c)Find the exact value of t at which the particle is instantaneously at rest.
Answer (c)[2]
(d)Find the displacement of the particle from O when it is instantaneously at rest, correct to 3 significant figures.
Answer (d)m[2]
(e)Find the total distance travelled by the particle in the first 4 seconds, correct to 3 significant figures.
Answer (e)m[3]
5
A particle P starts from a fixed point O with velocity −12 m/s and moves in a straight line. Its acceleration, a m/s², t seconds after leaving O, is given by a=8−2t, until it reaches its greatest velocity at t=T. After that it decelerates uniformly at 1.5 m/s² until it comes to rest.
(a)Find an expression for the velocity of P in terms of t, for 0≤t≤T.
Answer (a)[2]
(b)Find the time at which P is first at instantaneous rest.
Answer (b)s[2]
(c)Find the value of T.
Answer (c)s[1]
(d)Find the greatest velocity of P.
Answer (d)m/s[1]
(e)Find the time at which P comes to rest.
Answer (e)s[2]
(f)Find the total distance travelled by P.
Answer (f)m[4]
END OF PAPER
Answers and worked solutions
Question 1
(a)Answer: =45 m[3]
s=39t3−28t2+c=3t3−4t2+c0=0+cc=0s=3(3)3−4(3)2=45 m
(b)Answer: =11 m/s[3]
v=24t2+3t+c=2t2+3t+c−3=0+cc=−3v=2(2)2+3(2)−3=11 m/s
Question 2
(a)Answer: =308 m[3]
3t2−42t+120=03(t−4)(t−10)=0t=4 or t=10It turns back at t=4.s=33t3−242t2+120t=t3−21t2+120tWhen t=4, s=208When t=9, s=108Distance=∣208−0∣+∣108−208∣Distance=208+100=308 m
(b)Answer: =359 m[3]
t2−8t+12=0(t−2)(t−6)=0t=2 or t=6It turns back at t=2.s=3t3−28t2+12t=31t3−4t2+12tWhen t=2, s=332When t=5, s=35Distance=332−0+35−332Distance=332+9=359 m
v=dtdsv=2(3)t2−24(2)t+42(1)=6t2−48t+42At rest: v=0.6t2−48t+42=0t2−8t+7=0(t−1)(t−7)=0t=1 or t=7
Question 4
(a)Answer: 10 m/s[1]
When t=0, v=12e0−2=10 m/s
(b)Answer: −6 m/s²[2]
a=dtdv=−6e−2tWhen t=0, a=−6 m/s²
(c)Answer: t=2ln6[2]
12e−2t−2=0e−2t=61−2t=−ln6t=2ln6
(d)Answer: 12.8 m[2]
s=∫(12e−2t−2)dt=−24e−2t−2t+cs=0 when t=0, so c=24s=24−24e−2t−2tWhen t=2ln6, s=24−4−2(2ln6)=12.8 m (3 s.f.)
(e)Answer: 12.9 m[3]
The particle is at rest at t=2ln6≈3.584, and moves back towards O after that.When t=4, s=24−24e−2−8s=12.752Distance =12.833+(12.833−12.752)=12.9 m (3 s.f.)
Question 5
(a)Answer: v=−12+8t−t2[2]
v=∫(8−2t)dt=8t−t2+c1v=−12 when t=0, so c1=−12v=−12+8t−t2
(b)Answer: t=2 s[2]
−12+8t−t2=0t2−8t+12=0(t−2)(t−6)=0t=2 or t=6; the first is t=2 (and t=6 is after T)
(c)Answer: T=4 s[1]
The velocity is greatest when a=0:8−2T=0T=4
(d)Answer: 4 m/s[1]
v=−12+8(4)−(4)2=4 m/s
(e)Answer: t=320 s[2]
After t=4: v=4−1.5(t−4)v=0 when t−4=1.54t−4=38t=320
(f)Answer: 364 m[4]
s=∫(−12+8t−t2)dts=−12t+4t2−3t3 (as s=0 at t=0)At t=2, s=−332; at t=4, s=−316First stage: 332+(−316+332)=16Second stage (velocity falls uniformly from 4 to 0): 21×38×4=316Total distance =16+316=364 m