Deformation problems and melting of crystals
Answers are for parents and teachers.
1
Steel wire (E = 2·10¹¹ Pa): l₀ = 4 m, S = 1 mm², F = 100 N. Find Δl.
Δl = 100·4/(2·10¹¹·10⁻⁶) = 2·10⁻³ m = 2 mm
2
A wire’s strength limit is 6·10⁸ Pa and the working stress 2·10⁸ Pa. Find the safety factor.
3
3
A force of 500 N acts on a wire of cross-section 2 mm². Find the stress in MPa.
250
4
Why is 100 °C water not enough to melt copper? State copper’s melting point.
Copper melts at 1083 °C, far above 100 °C.
5
Why does the surroundings feel cold when snow melts?
Melting needs heat, which is taken from the surroundings.