Write what the core of transformer is. Explain the mutual induction process.

A bus starts from rest and accelerates uniformly to a speed of \( 80 \mathrm{~km} / \mathrm{h} \) in 4 hours It mainfains this speed It another 6 hours before decelerafing uniformly to rest in 3 hours. a) Draw a velocity - time graph to show the journey. b) Determine: i) The acceleration, in \( \mathrm{km} / \mathrm{h}^{2} \), during the first 4 hours ii) The retardation, in \( \mathrm{km} / \mathrm{h}^{2} \), during the last 3 hours. iii) The average speed for the entre journey in \( \mathrm{km} / \mathrm{h} \).

20. A periodic longitudinal wave that has a frequency of 20.0 Hz travels along a coiled spring toy. If the distance between successive compressions is 0.600 m , what is th speed of the wave?

When fring a rifle, the bullet (mass: 001 kg ) is shot forward wth an acceleration of \( 500 \mathrm{~m} / \mathrm{s}^{2} \). If the mass of the nfle is 4 kg . what is its recoil acceleration?

b) A rectangular watertight box is 475 mm long, 475 mm wide and 205 mm deep. It weighs 225 N . If it floats with its sides and ends vertical in water of density \( 1030 \mathrm{~kg} / \mathrm{m}^{3} \), what depth of the box will be submerged? Take the gravitational acceleration as \( 9.81 \mathrm{~m} / \mathrm{s}^{2} \).

When a constant force acts upon an object, the acceleration of the object varies inversely with its mass. When a certain constant force acts upon an object with nass 4 kg , the acceleration of the object is \( 19 \mathrm{~m} / \mathrm{s}^{2} \). If the same force acts upon another object whose mass is 38 kg , what is this object's acceleration?