Q 24, 25, 26 i dont get them and need answers for it

24) W = 75 [J]; 25) W = 1794[J]; 26) n = 8.8 (times) or 9 (times)

Explanation:

24) This problem can be solved by means of the following equation.

where:

DU = internal energy difference [J]

Q = Heat transfer [J]

W = work [J]  

Since there are no temperature changes the internal energy change is equal to zero

DU = 0

therefore:

The work is equal to the heat transfered, W = 75 [J].

25) The heat transfer can be calculated by means of the following equation.

Q = 0.4*897*5 = 1794[J]

Work is equal to heat transfer, W = 1794[J]

26) Each time the bag falls the potential energy is transformed into heat energy, which is released into the environment. In this way the potential energy is equal to the developed heat.

where:

m = mass = 0.5[kg]

g = gravity = 9.81[m/s^2]

h = 1.5 [m]

The heat developed can be calculated by means of the following equation.

The number of times will be calculated as follows

n = 65/7.36

n = 8.8 (times) or 9 (times)

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2