Unit 8 Worked More Answers...
s
1 2
gt
2
1
s  ut  at 2
2
v 2  2as  u 2
vu
s
t
 2 
v  u  at
Mr Powell 2009
Index
Problem Sheet 8.5
Mr Powell 2009
Index
Problem Sheet 1
Mr Powell 2009
Index
Problem Sheet 1
1)
2)
3)
4)
a 0.018s b) 0.036s
a) 10m/s2 bi) 45m bii) 3s c) 15s
a) 9.53m/s b) 10.27 m/s
60m
d) 18s)
e) 371.8m f) 123.2m
Mr Powell 2009
Index
2) (problem sheet 1)
Antelope & Cheetah
Velocity in m/s
30
450
45
18
3
Time in s
Mr Powell 2009
Index
Antelope & Cheetah
2) cont…. (problem sheet 1)
Velocity in m/s
22
Answer fits here to fill
in the unknown!
347.6
24.2
Now work out the total area
under graph for distance
travelled = 371.8
18
2.2
Time in s
Mr Powell 2009
Index
3) Is solved using simultaneous equations (problem sheet 1)
In a 100m race we know total s = s1+s2
Antelope & Cheetah
Velocity in m/s
v
S2
S1
1.5
10.49
Time in s
1) Set up two equations one for each part of journey
2) Add together and should = 100m
3) As final “V” is the same for both sub into equation
for s
4) Velocity v is found
Mr Powell 2009
Index
Problem Sheet 8.8
Use the simulation to help you….
Questions 1-3 simply use the
4th Law of Uniformly Accelerated Motion
v  2as  u
2
2
Questions 4-9 combine the 1st and 3rd
Laws of Uniformly Accelerated Motion
v  u  at
1 2
s  ut  at
2
NB: We should also be aware that gravitational attraction produces a force which, on
earth, causes a free-fall acceleration g of approximately 9.8 m/s2. Free vertical motion (or
freefall) is simply uniformly accelerated motion in which a = g = +/- 9.8 m/s2, depending on
the direction chosen as positive. (This assumes there are no resistive forces like air or water
resistance).
5) A cricket ball is thrown vertically upwards with a velocity of 20 m/s. Calculate
a) the maximum height reached.
b) the time taken to return to earth.
a)
b)
6) A ball is dropped from a cliff top and takes 3.0 s to reach the beach below. Calculate
a) the height of the cliff
b) the velocity acquired by the ball.
a)
S = 44.1m
b)
7) With what velocity must a ball be thrown upwards to reach a height of 15m?
8) A man stands on the edge of a cliff and throws a stone vertically upwards at 15 m/s.
After what time will the stone hit the ground 20m below?
1 2
s  gt
2
2s
t
g
2  (34.46  20)m
t
9.81
t  3.33s
9) A stone is thrown horizontally with a velocity of 3.0 m/s from the top of a
vertical cliff 200m high. There are no horizontal forces acting on the stone
(therefore acceleration in the horizontal direction is zero). The only vertical
force is that of gravity. Calculate;
a) how long it takes to reach the ground.
b) its distance from the foot of the cliff.
c) its vertical and horizontal components of velocity when it hits the ground.
9) A stone is thrown horizontally with a velocity of 3.0 m/s from the top of a
vertical cliff 200m high. There are no horizontal forces acting on the stone
(therefore acceleration in the horizontal direction is zero). The only vertical
force is that of gravity. Calculate;
a) how long it takes to reach the ground.
b) its distance from the foot of the cliff.
c) its vertical and horizontal components of velocity when it hits the ground.
Thrust SSC Answers
1
(a) (i)
(ii)
Uniform acceleration
Non-uniform acceleration
After 4 s, acceleration first increases (slightly) then decreases.
(NB NO deceleration, acceleration does NOT become negative)
(b) a = dv/dt = 180 m s-1/10 s
(or similar values read from tangent to graph on next slide) = 18.0 m s-1
(c) 100 small squares represent 1000 m area under graph is about 62 small
squares so displacement is about 1000 m x 62/100 = 620 m (or similar value deduced
from area of graph)
Mr Powell 2009
Index
Thrust SSC Answers
Mr Powell 2009
Index
Exam Book Questions...
Exam Question ...June 02 Spec A Q1
1) The graph below shows how the velocity of a toy train moving in a straight line
varies over a period of time. Describe the motion of the train in the following
regions of the graph.
AB
BC
CD
DE
EF
(5 marks)
Mr Powell 2009
Index
Exam Question ...June 02 Spec A Q1
1) The graph below shows how the velocity of a toy train moving in a straight line
varies over a period of time.
(b) What feature of the graph represents the displacement of the train? (1 mark)
(c) Explain, with reference to the graph, why the distance travelled by the train is
different from its displacement (2 marks
Mr Powell 2009
Index
Exam Question ...Jan 07 Spec A Q2
2 (a) A cheetah accelerating uniformly
from rest reaches a speed of 29ms-1 in
2.0 s and then maintains this speed for 15
s. Calculate
(i) its acceleration,
(ii) the distance it travels while
accelerating,
(iii) the distance it travels while it is
moving at constant speed.
(4 marks)
Mr Powell 2009
Index
Exam Question ...Jan 07 Spec A Q2
(b) The cheetah and an antelope are both at rest and 100 m apart. The cheetah
starts to chase the antelope. The antelope takes 0.50 s to react. It then accelerates
uniformly for 2.0 s to a speed of 25ms-1 and then maintains this speed. The graph
shows the speed time graph for the cheetah. (i) Using the same axes plot the speedtime graph for the antelope during the chase.
Mr Powell 2009
Index
Exam Question ...Jan 07 Spec A Q2
(b) The cheetah and an antelope are both at rest and 100 m apart. The cheetah
starts to chase the antelope. The antelope takes 0.50 s to react. It then accelerates
uniformly for 2.0 s to a speed of 25ms-1 and then maintains this speed. The graph
shows the speed time graph for the cheetah. (i) Using the same axes plot the speedtime graph for the antelope during the chase.
Mr Powell 2009
Index
Exam Question ...Jan 07 Spec A Q2
2 (a) A cheetah accelerating uniformly
from rest reaches a speed of 29ms.1 in
2.0 s and then maintains this speed for 15
s. Calculate
(i) its acceleration,
(ii) the distance it travels while
accelerating,
(iii) the distance it travels while it is
moving at constant speed.
(4 marks)
Mr Powell 2009
Index
Exam Question ...Jan 07 Spec A Q2
(b) The cheetah and an antelope are both at rest and 100 m apart. The cheetah
starts to chase the antelope. The antelope takes 0.50 s to react. It then accelerates
uniformly for 2.0 s to a speed of 25ms.1 and then maintains this speed. The graph
shows the speed time graph for the cheetah.
(ii) Calculate the distance covered by the antelope in the 17 s after the cheetah
started
to run.
(iii) How far apart are the cheetah and the antelope after 17 s?
Mr Powell 2009
Index