Questions in Newtons Laws and Thermodynamimcs.

[nasar176]

Hi there can anyone please explain to me these questions I am really confused about them.

Q: A 15 kg wagon is pulled to the right a force of 45 Newtons. the wagon accelarates at 2 m/s2. what is the net (unbalanced) force accelerating the wagon? (f of g is 10)

the book says the answer is 30, but i have no idea why?

Q: If 200 grams of water at 48 C is mixed with 100 grams of water at 30 c, the resulting temp. of the water is?

I wanted to use the mc(delta)t equation but they don't give the specific heat of water in the question.

Q: If all of the forces acting on an object balance so that the net force is zero, then:
A) the object must be at rest (i chose this answer but its wrong IDK why)
B)the object speed will decrease
c)
D)
E) none of the above( this is the answer according to the book.

Q: at the surface of the earth, an object of mass m has weight w. If this object is transported to an altitude that's twice the radius of the Earth then at the new location the mass and weight is?

i said the mass is m because its an intrinsic property but i don't know what the wieght would be.

please help me out, i am studying for a test and i really need to clear these concepts.
thanks

 

[dikmikkel]

Maybe. m=15 kg and the force F=45N, it accelerates by 2m/s/s then
$F_{net} = ma = 15\text{kg}\times 2\text{m/s^2} = 30 \text{N}$

 

[dikmikkel]

The 2nd question. Find it yourself, it must be this equation you are to use, else it is complicated I think.
3rd question: Newtons 1st law says that a particle which is affected by no force is continuing with the same velocity along a straight line, thus if it had e.g. v = 400m/s as velocity it would still be moving with that velocity not increasing nor decreasing.
4. I think you should use the gravitational formula $F_{grav} = -G\dfrac{mM_{earth}}{r}$ then compare that force to the usual F = mg

 

[nasar176]

ok thanks

 

[Nickie]

Hello, it seems like you have a few questions about Newton's Laws and thermodynamics. I will do my best to explain them to you.

For the first question, we can use Newton's Second Law which states that force (F) equals mass (m) multiplied by acceleration (a). In this case, we know the mass of the wagon (15 kg) and the acceleration it experiences (2 m/s^2). So, we can plug these values into the equation: F = m x a. This gives us F = 15 kg x 2 m/s^2 = 30 Newtons. This is the net force accelerating the wagon.

For the second question, we can use the formula for specific heat (c) which is the amount of heat required to raise the temperature of a substance by 1 degree Celsius. We know the mass of each water sample (200 g and 100 g) and the initial temperatures (48 C and 30 C). We also know that the final temperature will be the same for both water samples when mixed. So, we can set up an equation: m1 x c x (Tf - T1) = m2 x c x (T2 - Tf). Since the specific heat of water is the same, we can cancel it out and solve for Tf. This gives us Tf = (m1 x T1 + m2 x T2) / (m1 + m2) = (200 g x 48 C + 100 g x 30 C) / (200 g + 100 g) = 44 C. This is the resulting temperature of the water after mixing.

For the third question, you are correct in choosing option A. If all forces acting on an object are balanced, then the object must be at rest or moving at a constant velocity. It cannot be accelerating. So, the correct answer should be A. However, it is possible that the book is referring to a specific scenario in which the object is at rest but the forces are not balanced. In that case, the correct answer would be E.

For the fourth question, the mass of the object will remain the same since it is an intrinsic property. However, the weight will change. Weight is the force of gravity acting on an object, and it is directly proportional to the mass and the strength of gravity. As we move farther away from the Earth's surface, the strength of gravity decreases. So,