All categories

4 years ago

Julia pushes her sled up a hill. In which direction is the force of friction acting?

Physics

1 answer:

tangare [24]4 years ago

5 0

Answer:

The force of friction acts down the hill.

Explanation:

Friction is a type of force that always act only when there is relative motion of an object.

Friction always opposes the motion of the change in state of the body and always acts in the direction opposite to the direction of motion. If the object is at rest and no force is acting on it, there will no frictional force acting on it.

If the object is in motion, it will act in the opposite direction.

Here, Julia pushes her sled up a hill. So, the motion of the sled is up the hill. So, frictional force will act in the opposite direction (down the hill) to oppose the motion.

You might be interested in

Bird bones have air pockets in them to reduce their weight. This also gives them an average density significantly less than that

mixas84 [53]

Answer:

mas of water displaced = 41.4 g

Explanation:

Weight in air = True weight = 45 g

Apparent weight = 3.6 g

Apparent weight = True weight - Buoyant force

Buoyant force = 45 g - 3.6 g = 41.4 g

Weight of water displaced = Buoyant force

Weight of water displaced = 41.4 g dyne

mas of water displaced = 41.4 g

8 0

3 years ago

A hollow metal sphere is electrically neutral (no excess charge). A small amount of negative charge is suddenly placed at one po

ser-zykov [4K]

Answer:

b. The excess charge has distributed itself evenly over the outside surface of the sphere.

Explanation:

When a neutral hollow metal sphere is touched externally with a charge, the charge distributes itself evenly on the surface of the sphere. One thing to note here is that for a hollow sphere, the charges stays on the surface alone. This phenomenon is why the inside of airplanes are free from electric charge when struck by a lightning when they travel through a lightning storm.

4 0

3 years ago

An object moves 45m due East and then 15m due West, the total distance is

marshall27 [118]

Answer:30m east

Explanation: 45m-15m=30m, which cancels out the one to the west. All that is left is 30m east.

Is this a test/quiz btw?

6 0

3 years ago

Two metal disks, one with radius R1 = 2.45 cm and mass M1 = 0.900 kg and the other with radius R2 = 5.00 cm and mass M2 = 1.60 k

natima [27]

Answer:

part (a) $a_1\ =\ 2.9\ kg$

Part (b) $a_2\ =\ 6.25\ kg$

Explanation:

Given,

mass of the smaller disk = $M_1\ =\ 0.900\ kg$
Radius of the smaller disk = $R_1\ =\ 2.45\ cm\ =\ 0.0245\ m$

mass of the larger disk = $M_2\ =\ 1.6\ kg$
Radius of the larger disk = $R_2\ =\ 5.0\ cm\ =\ 0.05\ m$
mass of the hanging block = m = 1.60 kg

Let I be the moment of inertia of the both disk after the welding, $\therefore I\ =\ I_1\ +\ I_2\\\Rightarrow I\ =\ \dfrac{1}{2}(M_1R_1^2\ +\ M_2R_2^2)\\\Rightarrow I\ =\ 0.5\times (0.9\times 0.0245^2\ +\ 1.6\times 0.05^2)\\\Rightarrow I\ =\ 2.27\times 10^{-3}\ kgm^2$

part (a)

A block of mass m is hanging on the smaller disk,

From the f.b.d. of the block,

Let 'a' be the acceleration of the block and 'T' be the tension in the string.

$mg\ -\ T\ =\ mg\\\Rightarrow T\ =\ mg\ -\ ma\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,eqn (1)$

Net torque on the smaller disk,

$\therefore \tau\ =\ I\alpha\\\Rightarrow TR_1\ =\ \dfrac{Ia}{R_1}\\\Rightarrow T\ =\ \dfrac{Ia}{R_1^2}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,enq (2)$

From eqn (1) and (2), we get,

$mg\ -\ ma\ =\ \dfrac{Ia}{R_1^2}\\\Rightarrow a\ =\ \dfrac{mg}{\dfrac{I}{R_1^2}\ +\ m}\\\Rightarrow a\ =\ \dfrac{1.60\times 9.81}{\dfrac{2.27\times 10^{-3}}{0.027^2}\ +\ 1.60}\\\Rightarrow a\ =\ 2.91\ m/s^2$

part (b)

In this case the mass is rapped on the larger disk,

From the above expression of the acceleration of the block, acceleration is only depended on the radius of the rotating disk,

Let ' $a_2$ ' be the acceleration of the block in the second case,

From the above expression,

$\therefore a\ =\ \dfrac{mg}{\dfrac{I}{R_1^2}\ +\ m}\\\Rightarrow a\ =\ \dfrac{1.60\times 9.81}{\dfrac{2.27\times 10^{-3}}{0.05^2}\ +\ 1.60}\\\Rightarrow a\ =\ 6.25\ m/s^2$

5 0

3 years ago

PLEASE HELP I’m gonna go nuts with all the work I have to do for school and I’m about to breakdown I can’t handle this

Stella [2.4K]

Answer:

Explanation:

I'm not sure how to explain.

7 0

3 years ago