Ist Law of Thermodynamics Question 2 of 10
What is the change in internal energy if 20 J of heat is released from a system
and the system does 50 J of work on the surroundings?
Use AU = Q-W.
A. 30 J
B. 70 J
C. 30 J
D. -70J

Change in heat energy = -30 J

Explanation:

Given:

AU = Q-W

Heat energy Q = 20 J

Work done W = 50 J

Find:

Change in heat energy

Computation:

Change in heat energy = 20 J - 50 J

Change in heat energy = -30 J

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.