mechanics and materials

Question 1

difference between scalars and vectors

Answer 1

• scalars: magnitude only
• vectors: magnitude and direction

Question 2

examples of scalar quantities

Answer 2

• distance
• speed
• mass
• temperature

Question 3

examples of vector quantites

Answer 3

• displacement
• velocity
• force/weight
• acceleration

Question 4

how do you find the resultant vector?

Answer 4

pythagoras (only when perpendicular)

Question 5

how do you find the direction of a vector?

Answer 5

trigonometry (only when perpendicular)

Question 6

when would you use a scale drawing?

Answer 6

when the vectors have angles other than 90

Question 7

how do you resolve vectors?

Answer 7

• trigonometry
• horizontal (Fcosθ)
• vertical (Fsinθ)

Question 8

how can you show an object is in equilibrium?

Answer 8

• horizontal and vertical components equal zero
• scale drawing shows a closed triangle

Question 9

what is a moment?

Answer 9

• M=fd
• force multiplied by perpendicular distance from the line of action of the force to the point

Question 10

what is a couple?

Answer 10

• pair of coplanar forces
• equal in magnitude
• work in opposite directions

Question 11

how to find the moment of a couple?

Answer 11

force multiplied by perpendicular distance between lines of action of forces

Question 12

what is the principle of moments?

Answer 12

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

Question 13

what is the centre of mass?

Answer 13

point at which an object’s mass acts

Question 14

mass of a uniform object

Answer 14

exactly in the centre