Mechanics DONE

Question 1

A moment is the turning effect of a force about a point X. A fulcrum/ pivot/ axis of rotation is a point on an object about which a rotating can occur. State the equation for the moment of a force and the 3 things you must state to describe a moment.

Answer 1

Moment (Nm)= Force (N) x Perpendicular distance from the line of action of the force to point X (m)

Magnitude of moment
Direction of moment- anticlockwise/ clockwise
Point you are taking the moment about

Question 2

State what is meant by the lever arm.

Answer 2

Perpendicular distance from the line of action of the force to point X/ fulcrum/ pivot/ axis

Question 3

State what is meant by line of action of a force and point of application of a force.

Answer 3

Line of action of a force- line along which force acts

Point of application of a force- point on the object where the force is applied

Question 4

State the principle of moments.

Answer 4

For a body to be in rotational equilibrium, the sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point ( resultant moment is 0)

Question 5

State what is meant by torque and the sign convention for clockwise and anticlockwise moments.

Answer 5

Torque is the combined effect of 2 or more forces acting on an object
Clockwise moments are positive and anticlockwise moments are negative

Question 6

Couples tend to cause rotation but not translation. Define a couple in terms of forces acting on an object and give the equation for the torque of a couple. Is the torque affected by the location of the pivot point?

Answer 6

A couple is a pair of equal and opposite forces acting on an object, but not along the same line
Torque of couple (Nm)= One of the forces (N) x Perpendicular distance between the forces (m)
No

Question 7

Explain why a couple has no effect on the contact/ friction forces at the pivot point making reference to translational equilibrium.

Answer 7

Because there is no contact/ friction force needed to oppose the motion in order to keep the system in transitional equilibrium because it already is

Question 8

State the position of the centre of gravity of an object when it is in stable rotational equilibrium.

Answer 8

Centre of gravity directly above pivot point

Question 9

Define centre of gravity of an object.

Answer 9

The single point on an object that you can consider its whole weight to act through