How far should pencil held from a convex mirror of radius 80 cm to form an image one-half the size of the pencil?

The energy released by a chemical reaction can be measured using a calorimeter. when barium hydroxide octahydrate crystals are reacted with dry ammonium chloride inside of a coffee cup calorimeter, the temperature of the 18.00 g of water in the calorimeter decreases from 30.0°c to 8.0°c. the equation for calculating energy absorbed or released by a reaction is: where q is the energy released or absorbed, m is the mass of water in the calorimeter, cp is the specific heat of water, and δt is the observed temperature change. if the specific heat of liquid water is 4.19 j/g·°c, how much energy was absorbed by the reaction?

2. -/1 pointsserpse10 2.7.p.017.mi. an object moving with uniform acceleration has a velocity of 14.0 cm/s in the positive x direction when its x coordinate is 2.97 cm. if its x coordinate 2.85 s later is -5.00 cm, what is its acceleration? cm/s2 need ? read it master it

You are given a vector a = 125i and an unknown vector b that is perpendicular to a. the cross-product of these two vectors is a × b = 98k. what is the y-component of vector b?