Quantum Mechanics Answers

Given three vectors
a⃗ =−i⃗ −4j⃗ +2k⃗
,
b⃗ =3i⃗ +2j⃗ −2k⃗
,
c⃗ =2i⃗ −3j⃗ +k⃗
, calculate
a⃗ ⋅(b⃗ ×c⃗ )


−6
6

9


−9

Which of the follwing statements is correcct?

An object can have a constant velocity even though its speed is changing

An object can have a constant speed even though its velocty is changing

An object can have zero acceleration and eventually reverses its direction

An object can have constant velocity even though its acceleration is not zero

Which of the following correctly gives the direction of a vector product
c⃗ =a⃗ ×b⃗
?

If the right thumb points in the direction of
a⃗
and the other fingers point in the direction of
b⃗
, then the palm pushes in the opposite direction of
c⃗
If the right is held such that the curled fingers follow the rotation of
a⃗
into
b⃗
, then the extended right thumb points in the direction of
c⃗
If the left thumb points in the direction of
a⃗
and the other fingers point in the direction of
b⃗
, then the palm pushes in the direction of
−c⃗
The direction of retreat of the right-handed screw when turned from
a⃗
to
b⃗
through the smaller angle.

Two vectors
a⃗
and
b⃗
have components, in arbitrary units,
ax=3.2
,
ay=1.6
,
bx=0.5
,
by=4.5
. Find the angle between
a⃗
and
b⃗


33o

28o

57o

62o

When we describe the motion of an object we are dealing with the part of mechanics called

statics

translation

dynamics

kinematics

15 Which of the following physical concepts best explains why passengers in fast moving cars should always fasten their seat-belts?

inertia

terminal velocity

moment of inertia

acceleration

16 An observer can describe the motion of an object as "translational" if

the axes of the reference frame imagined to be attached to the object
x′
,
y′
and
z′
always remain parallel to the axes of his own reference frame
x
,
y
and
z
the object moves in a curved path in such a way that
x′
,
y′
and
z′
may rotate about their origin
O′
the motion of the object may not be represented by the motion of its centre of mass

all the constituent particles of the object undergo different displacements at the same time

17 An object is thrown upward from the edge of a building with a velocity of 20 m/s. Where will the object be 3s after it was thrown?


−22m
16m

22m


−16m

18 The displacement of a particle along the X-axis is given as
x=5t2+1
, where x is in metres and t in seconds. Calculate its average velocity in the time interval between 2 s and 3 s.

21 m/s

40 m/s

46 m/s

25 m/s

19 A bullet is straight upward with a velocity of 100 m/s from the top of a building 100 m high. Find its maximum height above the ground

500 m

600 m

1000 m

300 m