It takes force of 15 N to stretch an ideal spring of negligible mass 3.0 cm. The spring is placed on a frictionless horizontal tabletop with one end fixed. A small 50-g metal ball is placed at the free end.
By how much should the spring be compressed to set the ball in motion horizontally at a speed of
4.5 m/s?
A) 21 cm
B) 4.5 cm
C) 2.1 cm
D) 9.0 cm
E) 4.2 cm

**urgent** roberto plans to use two transformers to reduce a voltage of 120 v to 4 v. he uses a transformer that has 300 coils in the primary winding and 50 coils in the secondary winding. he has four other transformers, as listed in the table. which transformer should roberto use to have an ending voltage of 4 v? a- w b-xc- yd- z

Acarpenter builds an exterior house wall with a layer of wood 2.9 cm thick on the outside and a layer of styrofoam insulation 2.3 cm thick on the inside wall surface. the wood has k=0.080w/(m⋅k), and the styrofoam has k= 0.010 w/(m⋅k). the interior surface temperature is 19.0 ∘c , and the exterior surface temperature is -15.0 ∘c . a.)what is the temperature at the plane where the wood meets the styrofoam? celsius b.)what is the rate of heat flow per square meter through this wall? /m^2

A1.5m wire carries a 2 a current when a potential difference of 52 v is applied. what is the resistance of the wire?