# IB Physics:Student Problems:

Mechanics

Nov 14, 2013 (5 years and 3 months ago)

234 views

IB Physics:

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:

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

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:

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:

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:

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)

t
taken for the police car P

to draw
level with car S.

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

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

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

(2)

IB Physics:

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:

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:

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:

Student Problems:

Topic 2.1
-
2.2

9

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:

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

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:

Student Problems:

Topic 2.1
-
2.2

11

IB Physics: