Mechanics P1

Question 1

Difference between a scalar and vector quantity

Answer 1

• scalar: only magnitude

- vector: magnitude AND direction

Question 2

Give 3 examples of scalar quantities (any 3 from)

Answer 2

• speed
• distance
• mass
• energy

Question 3

Give 3 examples of vector quantities (any 3 from)

Answer 3

• velocity
• displacement
• force (weight)
• acceleration
• temperature
• momentum

Question 4

Convert Newtons (N) into SI units

Answer 4

F = ma
Newtons = kg x ms^-2
= kgms^-2

Question 5

SI unit for momentum

Answer 5

kgms^-1

Question 6

State the law of conservation of momentum

Answer 6

• in collisions, linear momentum is always conserved

- the total momentum before an action, is equal to the total momentum after the action

Question 7

State the law of conservation of energy

Answer 7

Energy cannot be created or destroyed, only transferred between stores

Question 8

How should you start with a momentum question

Answer 8

make the two sides of momentum equal to each other:

• if the two objects move off together:
  (m1 x v1i) + (m2 x v2i) = (m1 + m2) x v1+2f
• if the two objects move off separately:
  (m1 x v1i) + (m2 x v2i) = (m1 x v1f) x (m2 x v2f)

Question 9

what is the acceleration of the vertical component of a object in air

Answer 9

the acceleration will be 9.81 if the object is moving downwards or -9.81 if the object is moving upwards