Edexcel IGCSE Physics 1.18 Weight equation

Practise using W = mg to calculate weight, mass or gravitational field strength from balances, forces and diagrams.

Exam points

state or rearrange W = mg to calculate weight or mass using g in N kg^-1
draw weight as a labelled downward force arrow on an object diagram
convert mass changes in g to kg before calculating small forces using W = mg

[Maximum number: 2]

Diagram 1 shows the apparatus a student uses to investigate the bending of a wooden strip.

Part of the wooden strip is clamped to a table.
A load is fixed to the free end of the wooden strip, causing it to bend.

Diagram 1

The free end of the wooden strip is positioned a length, L , beyond the edge of the table, as shown in diagram 1.

The weight of the load causes the end of the wooden strip to move down through a height, h.

A student investigates how the length, L , affects the height, h .

The load has a mass of 250 g.

Calculate the weight of the load.
Use the formula

weight = mass x gravitational field strength, g

weight = ............ N

Marking points:
- substitution into formula
- evaluation

Example:
W=mg $W=\frac{250}{1000}\times10$ $W=2.5\ \mathrm{N}$

Accept:
- use of g=9.8 or 9.81
- 2.45 or $2.4525\ \mathrm{N}$

Ignore:
- units

Marking guidance:
- Deduct 1 mark for a clear power-of-ten error in units of mass.

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1.18 Weight equation question 1