Answer quickly please! Calculate the efficiency of the following devices:
a A lawnmower which converts 143 J out of every 450 J of electrical input
energy into sound and heat. The rest of the energy is converted to kinetic
energy of the blades attached to the motor.

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.