IB Physics:Student Problems:

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IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




1

Uniform Acceleration

1.

Which

one
of the following is a correct definition of
displacement
?

A.

Distance from a fixed point

B.

Distance moved from a fixed point

C.

Distance from a fixed point in a given direction

D.

Distance moved in a given direction

(1)

2.

An athlete runs round a circular track at constant speed. Which
one
of the following graphs best
represents the variation with time
t
of the magnitude
d
of the
displacement
of the athlete from
the starting position during one lap of the track?


(1)

3.

A ball is released from rest near the surface of the Moon. Which
one
of the following quantities
increases at a constant rate?

A.

Only distance fallen

B.

Only speed

C.

Only speed and distance fallen

D.

Only speed and acceleration

(1)




d
d
d
d
0
0
0
0
0
0
0
0
t
t
t
t
A.
C.
B.
D.
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




2

4.

A stone X is

thrown vertically upwards with speed
v

from the top of a building. At the same time,
a second stone Y is thrown vertically downwards with the same speed
v

as shown.



Air resistance is negligible. Which
one

of the following statements is
true

about the speeds with
which the stones hit the ground at the base of the building?

A.

The speed of stone X is greater than that of stone Y.

B.

The speed of stone Y is greater than that of stone X.

C.

The speed of stone X is equal to that of stone Y.

D.

An
y statement about the speeds depends on the height of the building.

(1)

5.

A stone is thrown horizontally from the top of a high cliff. Assuming air resistance is negligible,
what is the effect of gravitational force on the horizontal and on the vertical c
omponents of the
velocity of the stone?


Vertical component of velocity

Horizontal component of velocity

A.

increases to a constant value

stays constant

B.

increases continuously

stays constant

C.

increases to a constant value

decreases to zero

D.

increases continuously

decreases to zero

(1)




Building
X
Y
v
v
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




3

6.

This question is about projectile motion.


A marble is projected horizontally from the edge of a wall 1.8 m high with an initial speed

V
.



A series of flash photographs are taken of the marble. The
photographs are combined into a
single photograph as shown below. The images of the marble are superimposed on a grid that
shows the horizontal distance

x
and vertical distance

y
travelled by the marble.


The time interval between each image of the marble
is 0.10 s.


(a)

On the images of the marble at
x

= 0.5 m and
x

= 1.0 m, draw arrows to represent the
horizontal velocity

V
H

and vertical velocity

V
V
.

(2)



ground
1.8 m
V
0
–0.50
–1.0
–1.5
–2.0
0
0.50
1.0
1.5
2.0
x
/ m
y
/ m
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




4

(b)

On the photograph, draw a suitable line to determine the horizontal distance

d
from the
base of

the wall to the point where the marble hits the ground. Explain your reasoning.

.............................................................................................................................
........

.........................................
............................................................................................

(3)

(c)

Use data from the photograph to calculate a value of the acceleration of free fall.

.......................................................................
..............................................................

.............................................................................................................................
........

...........................................................
..........................................................................

(3)

(Total 8 marks)

7.

This question is about throwing a stone from a cliff.


Antonia stands at the edge of a vertical cliff and throws a stone vertically upwards.



The stone leaves Antonia’s hand with a speed
v

= 8.0ms

1
.


The acceleration of free fall
g

is 10 m s

2

and all distance measurements are taken from the point
where the stone leaves Antonia’s hand.

(a)

Ignoring air resistance calculate

(i)

the maximum heigh
t reached by the stone.

...........................................................................................................................

............................................................................................................
...............

(2)

(ii)

the time taken by the stone to reach its maximum height.

...........................................................................................................................

...........................................................................................................................

(1)

Sea
v =
8.0ms
–1
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




5


The time between the stone leaving Antonia’s hand and hitting the sea is 3.0 s.

(b)

Determine the height of the cliff.

........
.............................................................................................................................

.............................................................................................................................
.....
...

.............................................................................................................................
........

.............................................................................................................................
........

(3)

8.

This question is about linear motion.


A police car P

is stationary by the side of a road. A car S, exceeding the s
peed limit, passes the
police car P at a constant speed of 18 m s

1
. The police car P sets off to catch car S just as car S
passes the police car P. Car

P

accelerates at 4.5 m s

2

for a time of 6.0 s and then continues at
constant speed. Car P

takes a time

t
seconds to draw level with car S.

(a)

(i)

State an expression, in terms of
t
, for the distance car S travels in

t
seconds.

...........................................................................................................................

(1)

(i
i)

Calculate the distance travelled by the police car

P

during the first 6.0 seconds of its
motion.

...........................................................................................................................

................................
...........................................................................................

(1)

(iii)

Calculate the speed of the police car

P

after it has completed its acceleration.

...........................................................................................................................

...........................................................................................................................

(1)

(iv)

State an expression, in terms of t, for the distance travelled by the police car P
during the time that it is travelling at constant speed.

...................................................................................................................
........

(1)

(b)

Using your answers to (a), determine the total time

t
taken for the police car P

to draw
level with car S.

.............................................................................................................................
.......
.

.............................................................................................................................
........

........................................................................................................................
.............

(2)


IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




6

Graphs

1.

The graph below shows the variation with time of the distance moved by a car along a straight
road. During which time interval does the car have its greatest acceleration?


(1)

2.

The variation with time

t
of the speed

v
of a
car moving along a straight road is shown below.




Which area, S
1
, S
2

or S
3
, or combination of areas, represents the total distance moved by the car
during the time that its speed is reducing?

A.

S
1

B.

S
3

C.

S
1

+ S
3

D.

S
1

+ S
2

+ S
3

(1)




A
B
C
D
distance
moved
time
v
t
0
0
S
S
S
1
2
3
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




7


3.

The diagram below shows the variation with time
t

of the velocity
v

of an object.



Which
one

of the following graphs shows the variation with time
t

of the acceleration
a

of the
object?


(1)








v
t
0
0
a
a
a
a
t
t
t
t
0
0
0
0
0
0
0
0
A.
C.
B.
D.
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




8



4.

A ball is dropped from rest at time
t

= 0 on to a horizontal surface from which it rebounds.
Which

one
of the following graphs best shows the variation of
speed

v

of the ball with time
t

from the time
t

= 0 to the time that the ball leaves the surface?



0
0
0
0
v
v
v
v
0
0
0
0
t
t
t
t
A.
C.
B.
D.
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




9

Answers

Uniform acceleration

1.

C

[1]

2.

C

[1]

3.

B

[1]

4.

C

[1]

5.

B

[1]

6.

(a)



Mark both together.

V
H

: horizontal arrows equal in length;

V
V

: two vertical arrows, the one at 1.0 m noticeably longer than the one at 0.5 m;

2

If arrows correct but wrong point(s) award
[1]
.

(b)

curve

that goes through all data points;

stops at
y
= 1.8m as this is the height of the wall;

from graph
d =
1.5(± 0.1)m;

3



0
–0.50
–1.0
–1.5
–2.0
0
0.50
1.0
1.5
2.0
x
/ m
y
/ m
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




10

(c)

travels vertically 1.8m in 0.6s /1.25m in 0.5s;

g

=
;

to give
g

= 10 (±1) m s

2
;

3

Award
[2 max]
for any time shorter than 0.5 s.

[8]

7.

(a)

(i)

h

=
;

to give
h

= 3.2 m;

2

(ii)

0.80 s;

1

(b)

time to go from top of cliff to the sea = 3.0


1.6 = 1.4 s;

recognise to use
s

=
ut

+
at
2

with correct substitution,

s

= 8.0 × 1.4 + 5.0 × (1.4)
2
;

to give
s

= 21 m;

3

Answers might find the sp
eed with which the stone hits the sea
from v = u + at, (42 m s

1
) and then use v
2

= u
2

+ 2as.

[6]

8.

(a)

(i)

18
t
;

1

(ii)

s

=

× 4.5 × 6
2

= 81m;

1

(iii)

v

=
at

= 6 × 4.5 = 27 m s

1
;

1

(iv)

27(
t



6);

1

(b)

idea of (a) (i) = (a) (ii) + (a) (iv);

18
t

= 81 + 27(
t



6)

t

= 9.0 s;

2

[6]

Graphs

1.

B

[1]

2.

C

[1]

3.

D

[1]

4.

A

[1]






2
2
t
s
g
v
2
2
2
1
2
1
IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




11



IB Physics:

Grade 11

Student Problems:

Topic 2.1
-
2.2




12