Velocity and force formulae

Velocity and force formulae

Pencil and paper
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Using this Resource
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Marking Student Responses
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Further Resources
This task is about using substitution to solve equations with given values.
 
 
Wikitoria found some mathematical equations in a textbook. For each equation she knew the value of all but one of the variables.
For the following equations, work out the value of the missing variable.
 

a)

The first equation gives a formula for the velocity (v) of a car.
 
 

v = u + at
where u = 20
           t = 4
           a = 9
 
 
What is the value of v? __________

 
b) The next equation gives the force (F) on a ball that is being kicked.
 
 

where m = 5
           v = 45
           u = 15
           t = 3 
   
What is the value of F? __________
Task administration: 
This task is completed with pencil and paper only.
Level:
5
Curriculum info: 
Maths, Number and Algebra, Equations and expressions
Keywords: 
substitution, equations
Description of task: 
Students use substitution to calculate a missing variable in algebraic expressions of practical situations.
Learning Progression Frameworks
This resource can provide evidence of learning associated with
Using symbols and expressions to think mathematically, sets 6-7
within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.
Answers/responses: 
 

Y10 (11/1999)

a)

56

easy

b)

50

easy
Diagnostic and formative information: 

  

Common error

Likely calculation

Likely reason

a)

33

20 + 4 + 9

Calculates u + a + t
Next steps: 

EXTENSION:

(Algebra / Science – physical world)
Use the equation v = u + at to show that the equation   is equivalent to the more usual form of F = ma.
 

ANSWER:

Rearrange the first equation to and substitute this into the other equation to get F = ma.

NOTE:   is equivalent to the change in speed per unit time = acceleration.