Concepts Of Physics MCQ Edition [Volume 2]PhysicsCalorimetry
A 50 kg man is running at a speed of 18 km h ⁻¹ . If the entirety of the man's kinetic energy is utilized to raise the temperature of water from 20^ C to 30^ C , what mass of water can be heated with this energy?
Options
- A15 g
- B30 g
- C7.5 g
- D15 kg
Correct answer
A. 15 g
Step-by-step solution
Velocity of the man, v = 18 km h ⁻¹ = 18 5 18 m s ⁻¹ = 5 m s ⁻¹ Kinetic energy of the man, K = 1 2 mv^2 K = 1 2 50 (5)^2 = 625 J This kinetic energy is utilized to heat the water. The heat energy required is given by Q = m_w s T Given T = 30^ C - 20^ C = 10^ C and specific heat of water s 4.18 J g ⁻¹ ^ C ⁻¹ Equating kinetic energy to heat energy: 625 = m_w 4.18 10 m_w = 625 41.8 g 14.95 g Rounding to the nearest integer, the mass of water that can be heated is 15 g .