A particle of mass m uniformly accelerates as counterclockwise along the circumference of a circle of radius R : r → = i ^ R cos θ + j ^ R sin θ with θ = ω 0 t + 1 2 α t 2 , where the constants ω 0 and α are the initial angular velocity and angular acceleration , respectively. Determine the object’s tangential acceleration a → t a n and determine the torque acting on the object using ( a ) τ → = r → × F → , ( b ) τ → = I α → .
A particle of mass m uniformly accelerates as counterclockwise along the circumference of a circle of radius R : r → = i ^ R cos θ + j ^ R sin θ with θ = ω 0 t + 1 2 α t 2 , where the constants ω 0 and α are the initial angular velocity and angular acceleration , respectively. Determine the object’s tangential acceleration a → t a n and determine the torque acting on the object using ( a ) τ → = r → × F → , ( b ) τ → = I α → .
A particle of mass m uniformly accelerates as counterclockwise along the circumference of a circle of radius R:
r
→
=
i
^
R
cos
θ
+
j
^
R
sin
θ
with
θ
=
ω
0
t
+
1
2
α
t
2
, where the constants
ω
0
and α are the initial angular velocity and angular acceleration, respectively. Determine the object’s tangential acceleration
a
→
t
a
n
and determine the torque acting on the object using (a)
τ
→
=
r
→
×
F
→
, (b)
τ
→
=
I
α
→
.
Definition Definition Rate of change of angular velocity. Angular acceleration indicates how fast the angular velocity changes over time. It is a vector quantity and has both magnitude and direction. Magnitude is represented by the length of the vector and direction is represented by the right-hand thumb rule. An angular acceleration vector will be always perpendicular to the plane of rotation. Angular acceleration is generally denoted by the Greek letter α and its SI unit is rad/s 2 .
4.) The diagram shows the electric field lines of a positively charged conducting sphere of
radius R and charge Q.
A
B
Points A and B are located on the same field line.
A proton is placed at A and released from rest. The magnitude of the work done by the electric field in
moving the proton from A to B is 1.7×10-16 J. Point A is at a distance of 5.0×10-2m from the centre of
the sphere. Point B is at a distance of 1.0×10-1 m from the centre of the sphere.
(a) Explain why the electric potential decreases from A to B. [2]
(b) Draw, on the axes, the variation of electric potential V with distance r from the centre of the
sphere.
R
[2]
(c(i)) Calculate the electric potential difference between points A and B. [1]
(c(ii)) Determine the charge Q of the sphere. [2]
(d) The concept of potential is also used in the context of gravitational fields. Suggest why scientists
developed a common terminology to describe different types of fields. [1]
3.) The graph shows how current I varies with potential difference V across a component X.
904
80-
70-
60-
50-
I/MA
40-
30-
20-
10-
0+
0
0.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VIV
Component X and a cell of negligible internal resistance are placed in a circuit.
A variable resistor R is connected in series with component X. The ammeter reads 20mA.
4.0V
4.0V
Component X and the cell are now placed in a potential divider circuit.
(a) Outline why component X is considered non-ohmic. [1]
(b(i)) Determine the resistance of the variable resistor. [3]
(b(ii)) Calculate the power dissipated in the circuit. [1]
(c(i)) State the range of current that the ammeter can measure as the slider S of the potential divider
is moved from Q to P. [1]
(c(ii)) Describe, by reference to your answer for (c)(i), the advantage of the potential divider
arrangement over the arrangement in (b).
1.) Two long parallel current-carrying wires P and Q are separated by 0.10 m. The current in wire P is 5.0 A.
The magnetic force on a length of 0.50 m of wire P due to the current in wire Q is 2.0 × 10-s N.
(a) State and explain the magnitude of the force on a length of 0.50 m of wire Q due to the current in P. [2]
(b) Calculate the current in wire Q. [2]
(c) Another current-carrying wire R is placed parallel to wires P and Q and halfway between them as shown.
wire P
wire R
wire Q
0.05 m
0.05 m
The net magnetic force on wire Q is now zero.
(c.i) State the direction of the current in R, relative to the current in P.[1]
(c.ii) Deduce the current in R. [2]
Chapter 11 Solutions
Physics for Scientists & Engineers with Modern Physics [With Access Code]
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