1.

(a) A 10 kg cat spends 40 kJ of energy to walk 1 km on a horizontal surface. What is the internal energy change of the cat caused by walking 1 km on a horizontal surface? Be specific about the sign (positive or negative). The efficiency of the cat to convert chemical energy from fats and sugars in the body into work is around 15%.

(b) The same cat now walks 1 km (horizontally) and at the end climbs up a tree so that it ends up 10 m higher than the horizontal surface. In the entire process, it used 60 kJ of energy. What is the internal energy change of the cat in this case? Approximate gravity acceleration as 10 m/s2. Be specific about the sign (positive or negative).