2020-2021 sem2_PHYS1005 midterm (1).pdf - Midterm Exam...

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1Midterm Exam (PHYS1005, 2020-2021, semester 2)Name:Student number:Useful constants:The gravitational constant of Earth:g= 10 m/s2The square of the speed of light:c2= 931.494 MeV/u1.A student eats a big dinner that is 1500 Calories and he wishes to expend the same amount of energyby exercising in the gymnasium. He decides to exercise by lifting a 50 kg barbell and he can raise thebarbell up by 2 meters each time. How many times does he have to raise the barbell in order to expendthe calories that he eats for dinner?[7 marks]2. A cowboy fires a silver bullet at a speed of 200 m/s into a wall. Assume the impact converts all thebullet’s kinetic energy to heat and the heat remains with the bullet. What is the temperature change ofthe bullet? The specific heat capacity of silver is 234 J/kgqC.[8 marks]3.When electric current moves in a conductor of resistance, it generates heat. This is a phenomenonoften called “joule heating” and is theworking principle of an electric heater. If the electric heater hasa total resistance of 20:and a voltage of 110 V is applied to it,(a).What is the current of this electric heater?

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