Fig. 4 What numbered position will provide the maximum torque?.

There is a piece of iron placed on a float. The magnet, marked as NS exerts an attractive force on the iron. The body gets pulled to the magnet without a twist.

Explain what may happen when shifted to numbered spots.

From this simple experiment we realise it is not only the magnitude and direction of a force that affects the motion of an object but the distance from force to the axle or the centre of mass is also crucial.

Torque considers all these 3 factors, namely direction, magnitude and the distance from the axle.

Thus the formula Torque = Force x radius. ( Radius being the distance to the rotating axis.

. τ = F r

Answer= Number 1 position. ( Reason- highest r value.)

**Rotational Inertia**

Inertia is the reluctance to accelerate. For linear motion, mass
is the only factor that determines inertia.
In rotatory motion it is the unbalanced torque that causes acceleration
and inertia is what offers reluctance.

1.1 What is a Radian ?
.a – An angle. .b. A
distance. .c – A force .d. Energy.

1.2
How many radians are there in a single rotation?

.a. 2 π. .b - 2 π r.
.c - 360 ˚ .
.d - 57.

1.3 How much is 1 radian in degrees?

.a – 45 ˚
.b - 2 π x 360 ˚
.c - 6.28 x r ˚.
.d – 360/2 π ˚.

1.4 .a,b,c and d
are equal forces acting in the horizontal plane on the oval shaped object. The
ob

ject is a flat disc fixed to an axle on one side. In your opinion which force
will produce the maximum torque?

1.5 Referring to diagram in

question 1,4 which force will produce the minimum torque?

2.0
**Fig. Measuring
distance.**

A wheel attached to a handle is sometimes used
to measure a distance. . It had a radius of 0.25 m.. In 2
minutes the wheel rotated 30 times while
pushing

Find the
following.

2.1 Time taken
for one complete revolution,

2.2 Angular
velocity.

2.3 Average
velocity of the man.

3.0

**Fig. **

**Wheels ****Bicycle .**
According to the
specifications given find the following: Neglect friction.

Force on
pedal =
25 N.

The pedal arm =
0.16 m. .

Radius large cog
wheel. ˚0.08 m,

Radius small cog wheel = 0.04 m

3.1. Torque on
the pedal.

3.2 Tension
force on chain.

3.3 How many times will the rare wheel turn for 1
turn of the pedal ?

3.4 The distance cycle willtravel.

4.0

The graph indicates
how an electric fan started to rotate when switched on. Find the following.

4.1 Average angular acceleration for the first 4 seconds.

4.2 Angular acceleration for last two seconds.

4.3 The number
of revolutions for the first 5 seconds.

4.4 The number
of revolutions for the last 2 seconds.

4.5 If the fan
had a blade 0.24 m long the linear speed
of its outer most edge.