What is the change in internal energy if 60J of heat are released from a system and 20J of work is done on the system? Use U=Q-W

1) What kind of energy is gained when your roller coaster goes uphill?

Dvinal [7]

1) Gravitational potential energy

In fact, gravitational potential energy is given by: $GPE=mgh$

where m is the mass of the roller coaster, g is the gravitational acceleration and h is the heigth. Therefore, when the roller coaster goes uphill, the height h increases and the roller coaster gains gravitational potential energy.

2) The relationship between potential and kinetic energy is:

$M.E.=K.E.+G.P.E.$

where ME is the total mechanical energy, KE is the kinetic energy, GPE is the gravitational potential energy. Since the value of ME is constant (when no friction is present), this means that when KE increases, GPE decreases, and vice-versa.

3) If friction is removed from the track, the roller coaster would move forever. In fact, in the equation written in part 2), ME is constant only in case there is no friction - when friction is present, part of the energy is lost due to the friction, so the total ME available decreases little by little until it becomes zero, and the roller coaster cannot move anymore.

4) It matters because it affects the magnitude of the friction. In fact, friction is given by

$F=\mu mg$

where $\mu$ is the coefficient of friction, m is the mass ,and g the gravitational acceleration. When the number of carts is increased, the mass increases, therefore the friction increases as well.

4 0

3 years ago

Read 2 more answers

While chatting with a friend you place your book bag on a nearby slide in the playground at school. The bag remains stationary.

alukav5142 [94]

Answer:

3. fs < μmg

4. fs = mg sinθ

Explanation:

For any object placed on a slide, there are 3 external forces acting on it:

Fg = m*g (always downward)
N (normal force, always perpendicular to the surface of the slide. going upward)
Fs (Friction Force, always opposite to the movement of the object, parallel to the slide)

As we have only one force with components along the normal and parallel to the slide directions (gravity force), it is advisable to find the components of this force, along these directions.

If θ is the angle of the slide above the horizontal, we have the following components of Fg:

Fgn = m*g*cosθ

Fgp = m*g*sin θ

We can apply Newton's 2nd Law to these perpendicular directions:

Fp = m*g*sin θ - Fs

Fn = N -m*g*cosθ = 0 (as the object has no movement in the direction perpendicular to the slide) (1)

Looking at the equation for the parallel direction, we have two forces, the component of Fg along the slide (which tries to accelerate the object towards the bottom of the slide), and the friction force.

While the object remains stationary, the equation for Newton's 2nd Law along this direction is as follows:

m*g*sin θ - fs =0 ⇒ fs = m*g*sinθ (4.)

This force can take any value (depending on the angle θ) to equilibrate the component of Fg along the slide, up to a limit value, which is given by the following expression:

fsmax = μN (2)

From (1), N= m*g*cos θ

Replacing in (2):

fsmax = μ*m*g*cos θ

While the bag remains at rest, we can say:

fs < μ*m*g*cosθ < μ*m*g (as in the limit cosθ =1)

So, the following is always true:

fs < μmg (3.)

6 0

3 years ago

Michael is looking for examples of energy at the park. He notices a mother pushing her child on a swing. He graphs the number of

inn [45]

Answer:

D.

Explanation:

As you see, the graph INCREASES, which means it goes up. It is not going down, only rising.

If I'm wrong forgive me ;-;

6 0

3 years ago

A basic physics question

Anna71 [15]

No,kinetic energy cannot be negative since its given by KE=mv²,mass cannot be negative and the square of speed cannot b negative.

Yes,any force opposing motion or displacement does negative work. They are often referred to as resistive forces (friction,air resistance,drag...)

Nope it does not, it just forces the object to move in a circular path known as a centripetal force. It can accelerate an object by changing it's direction but not it's speed.

No it cannot,If an object is sliding on the table (assuming it is not an incline), then most probably that normal force cancels out the weights effect or assuming there is an incline, it cancels the weight's y component.

$w = f.d.cos \alpha = f.d.cos90 = 0$