3.4.1 - Mechanics

Question 1

What are some examples of scalar quantities?

Answer 1

distance, speed, mass, temperature

Question 2

What are some examples of vector quantities?

Answer 2

displacement, velocity, force/ weight, acceleration, energy

Question 3

How do you calculate moments?

Answer 3

force x perpendicular distance to line of action of force from the point

Question 4

What are the units of moments

Answer 4

Nm

Question 5

what can a couple NOT do?

Answer 5

produce translational motion

Question 6

How do you find the moment of a couple?

Answer 6

force x perpendicular distance between the lines of action of forces

Question 7

What does the principle of moments state?

Answer 7

for an object in equilibrium, the sum of anticlockwise moments about a pivot is equal to the sum of clockwise moments

Question 8

What does it mean if an object is described as uniform?

Answer 8

its centre of mass is exactly at the centre

Question 9

What is the gradient of a displacement-time graph equal to?

Answer 9

velocity

Question 10

How do you find the average velocity?

Answer 10

divide the final displacement by the time taken

Question 11

How do you find the velocity from an acceleration-time graph?

Answer 11

area under the graph

Question 12

How do you find acceleration from a velocity-time graph?

Answer 12

the gradient

Question 13

How do you find displacement from a velocity-time graph?

Answer 13

area under the graph

Question 14

What is free fall?

Answer 14

when an object experiences only an acceleration of g (approx. 9.81ms^-2)

Question 15

What do frictional forces do?

Answer 15

convert kinetic energy into other forms, such as heat and sound

Question 16

How can we see terminal speed with a skydiver?

Answer 16

As they leave the pane, they accelerate because their weight is greater than the air resistance. As the skydiver’s speed increases, the magnitude of air resistance also increases. This continues until the force of weight and air resistance become equal, at which point terminal velocity is reached.

Question 17

How does air resistance affect the horizontal and vertical projectile motion?

Answer 17

the maximum height is reached earlier and both the vertical and horizontal distances travelled decrease

Question 18

What is true of momentum?

Answer 18

it is always conserved in any interaction where no external forces act, so the momentum before an event = the momentum after.

Question 19

What is force equal to?

Answer 19

the rate of change of momentum

Question 20

What is impulse and what is its equation? Where is it found on a force-time graph?

Answer 20

it is the change in momentum
F x t
the area under the graph

Question 21

What is Newton’s first law?

Answer 21

An object will remain in its current state of motion, unless acted on by a resultant force.

Question 22

What is Newton’s second law?

Answer 22

The sum of the forces acting on an object is equal to the rate of change of momentum of the object.

Question 23

What is Newton’s third law?

Answer 23

Every action has an equal and opposite reaction.

Question 24

What is the principle of moments?

Answer 24

For an object to be in equilibrium, the sum of the clockwise moments acting about a point must be equal to the sum of the anticlockwise moments acting about the point.