Mechanics

Question 1

Define Moment

Answer 1

It is the turning effect of a force. It can be explained by the equation: Moment = Force x perpendicular distance from the pivot.

Question 2

Unit of Moment

Answer 2

Newton meter (Nm)

Question 3

What is Couple?

Answer 3

A pair of equal and opposite Copland forces that has a turning point but no resultant force.

Question 4

Define Center of Mass.

Answer 4

The point at which the weight of the object may be considered to act.

Question 5

Discuss an object stability using the Center of Mass.

Answer 5

An object is stable when its center of mass is inside its base (it will topple if its center of mass is outside its base). The wider base an object has, the lower its center of mass, the more stable it is.

Question 6

Using your knowledge of the centre of mass, explain why would a forklift truck be better carrying its load close to the ground, rather than higher up in the air.

Answer 6

As the mass of the load is lowered towards the ground, the centre of mass of the load and the truck moves towards the ground. This improves the stability of the load and forklift truck.

Question 7

Define Displacement.

Answer 7

The distance moved by an object in a specific direction (Vector quantity).

Question 8

Define Velocity.

Answer 8

The rate of change of displacement.

Question 9

What is instantaneous velocity?

Answer 9

The specific velocity of an object at a specific point in time. It can be found from a displacement-time graph by drawing a tangent to the graph at the specific time and calculating the gradient.

Question 10

What is average velocity?

Answer 10

The velocity of an object over a specific time. It can be found by dividing the the final displacement by the time taken.

Question 11

Define acceleration.

Answer 11

The rate of change of velocity of an object.

Question 12

Displacement-Time Graph.

Answer 12

Gradient: velocity
Area under graph: MEANINGLESS
Y-intercept: initial displacement
Straight line: constant velocity
Curved line: acceleration
Horizontal line: stationary

Question 13

Velocity-Time Graph.

Answer 13

Gradient: acceleration
Area under graph: displacement
Y-intercept: initial velocity
Straight line: uniform acceleration
Curved line: non uniform acceleration
Horizontal line: constant velocity

Question 14

Acceleration-Time Graph

Answer 14

Gradient: MEANINGLESS
Area under graph: change in velocity
Y-intercept: initial acceleration
Straight line: constant acceleration
Curved line: none
Horizontal line: stationary

Question 15

What Force would act on an object in free fall?

Answer 15

If an object is in free fall, then the object’s weight is the only force acting on it. It will accelerate at a constant rate. This constant rate is called the acceleration due to gravity (g).

Question 16

What is drag?

Answer 16

Drag is a frictional force experienced by objects that travel through liquid or gas. The faster an object moves through a medium, the larger the drag.

Question 17

What happens to projectile motion if air resistance isn’t negligible?

Answer 17

The horizontal component of the velocity of a projectile decreases which means that both its range and maximum height is decreased compared to no air resistance.

Question 18

State Newton’s First Law.

Answer 18

An object will remain at rest or continue moving with constant velocity unless acted on by a resultant force.

Question 19

State Newton’s Second Law.

Answer 19

The resultant force on an object is equal to its rate of change in momentum

(Or)

The resultant force on an object with constant mass is directly proportional to its acceleration.

F (resultant force) = m (mass) x a (acceleration)

Question 20

State Newton’s Third Law.

Answer 20

If body A exerts a force on body B, then body B will exert a force on body A of equal magnitude but in the opposite direction

Question 21

Rules on Newton’s third law pairs:

Answer 21

• The two force pairs must act on two different objects.
• Must be of the same type.
• Must have the same magnitude but opposite direction.

Question 22

What does it mean by closed systems?

Answer 22

Systems with no external forces may be described as ‘closed’ or ‘isolated’