Energy Conversation States
TMA03 Covering Block 3
Question 1
(a) An impactor mass of 45 kg is used to represent the weight of child reasonably regarded to be involved in an accident with glass or plastics.
(b) The BS standards gives the manufacturers a clear set of standards that their products need to achieve to be safe and fit for the purpose that they have been designed for. It also gives the purchaser the expectation that the item has reached the standards set down by the BSI and will be a safe for the expected life of the item.
(c) (i) The energy on impact is calculated by using the following equations:
Potential Energy (PE) = mass x gravity x height
This gives the potential energy at the height when the ball is held at the start of the test. This can be used as a check to for the Kinetic energy (KE) equation as the law of energy conversation states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system is a constant. So the PE when the ball is held at height will be the same as the KE just before the impact with the glass.
To calculate the KE use the equation
KE = ½mv2
(ii)
Using the KE equation from question (i)
KE = ½mv2
|u = initial velocity |
|v = final velocity |
|a = acceleration |
|s = distance |
Insert the constants of
Mass = 45kg
To calculate the v2 using the equation
v2 = u2 + 2 x a x s
For test 1
KE = ½mv2
For the v2
v2 = 02 + 2 x 9.8 x 305
Gives 5978
Insert in to KE = ½mv2 to give
KE = ½ x 45 x 5978
To give 134505 = 135J to 3 sf
To check use PE = mgh
45 x 9.8 x 305 = 134505
Round up to 3 sf to give 135 J
Question 1
(a) An impactor mass of 45 kg is used to represent the weight of child reasonably regarded to be involved in an accident with glass or plastics.
(b) The BS standards gives the manufacturers a clear set of standards that their products need to achieve to be safe and fit for the purpose that they have been designed for. It also gives the purchaser the expectation that the item has reached the standards set down by the BSI and will be a safe for the expected life of the item.
(c) (i) The energy on impact is calculated by using the following equations:
Potential Energy (PE) = mass x gravity x height
This gives the potential energy at the height when the ball is held at the start of the test. This can be used as a check to for the Kinetic energy (KE) equation as the law of energy conversation states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system is a constant. So the PE when the ball is held at height will be the same as the KE just before the impact with the glass.
To calculate the KE use the equation
KE = ½mv2
(ii)
Using the KE equation from question (i)
KE = ½mv2
|u = initial velocity |
|v = final velocity |
|a = acceleration |
|s = distance |
Insert the constants of
Mass = 45kg
To calculate the v2 using the equation
v2 = u2 + 2 x a x s
For test 1
KE = ½mv2
For the v2
v2 = 02 + 2 x 9.8 x 305
Gives 5978
Insert in to KE = ½mv2 to give
KE = ½ x 45 x 5978
To give 134505 = 135J to 3 sf
To check use PE = mgh
45 x 9.8 x 305 = 134505
Round up to 3 sf to give 135 J