Which of the following is true? *

a backpack has a mass of 8 kg. it is lifted and given 54.9 J of gravitational potential energy. how high is is lifted? accelerat

dalvyx [7]

P=mgh
h=P/mg
h=(54.9)/(8*9.8)= 0.7m

8 0

2 years ago

describe how the volume of a floating object such as a cork can be found.fully describe please step by step.

Rama09 [41]

Answer:

Explanation:

Use Archimedes' principle, that states something of this nature: "The buoyant force acting on an object immersed in a fluid is equal to the weight of the fluid displaced"

Say, you take a cube of wood(for example) and place it in a bucket of water. Your cube is bound to sink, until, the upthrust force equals its weight.

Where does this upthrust come from?

As the cube sinks, it displaced some volume of water(if the bucket were full you would see water pouring out)

Archimedes simply stated that: Upthrust,

U=mg

Example: One way to measure the volume of any irregular object (in your case, a stone) is to submerge it completely under water and measure the change in the height of the water level. This change in the water level (let's say it goes from 50 mL to 65 mL) indicates that the stone has a volume of 15 mL.
Example:Subtract the first volume from the second volume to calculate the volume of the stone. For example, if you recorded 40 fluid ounces the first time, and 50 fluid ounces the second time, the stone volume is 10 fluid ounces.

7 0

2 years ago

A textbook of mass 2.05 kg rests on a frictionless, horizontal surface. A cord attached to the book passes over a pulley whose d

blsea [12.9K]

Answer:

a. 7.38 N b. 40.87 N c. 0.113 kg-m²

Explanation:

a. Let T be the tension in the cord. For the textbook, T = ma since no other force acts on it and it is an horizontal force, and m = mass = 2.05 kg and a = acceleration. We find the acceleration from s = ut + 1/2at² where u = initial speed = 0 (since it starts from rest), s = distance moved = 1.30 m and t = time = 0.850 s.

Substituting these values into s,

1.30 m = 0 × 0.850 + 1/2a × 0.850² = 0 + 0.36125a

1.30 = 0.36125a

a = 1.30/0.36125 = 3.6 m/s²

Substituting this into T, we have

T = ma = 2.05 kg × 3.6 m/s² = 7.38 N

b. Let T be the tension in the cord attached to the book. The book has the only vertical forces acting on it as the tension, T(acting upwards) and its weight mg (acting downwards). So the net force acting on it is

T - mg = ma

T = m(a + g)

substituting a = 3.6 m/s² and g = 9.8 m/s² and m = 3.05 kg

T = 3.05(3.6 + 9.8) = 3.05 × 13.4 = 40.87 N

c. Since the tangential acceleration of the pulley is also the acceleration of the masses, the a = rα where r = radius of pulley = 0.200 m/2 = 0.100 m and α = angular acceleration of the pulley.

α = a/r = 3.6 m/s² ÷ 0.100 m = 36 rad/s²

Now, the torque on the pulley τ = Tr = Iα where I = moment of inertia of pulley about its rotational axis and T = tension in cord attached to book and r = radius of pulley = 0.200 m/2 = 0.100 m

From the equation above, I = Tr/α

Substituting the variables we have

I = 40.87 N × 0.100 m ÷ 36 rad/s² = 0.113 kg-m²

4 0

3 years ago

Read 2 more answers

Some of the energy the car gained as it was pulled was lost because of heat from friction. The rest of the energy was transforme

Lisa [10]

Answer:

454,320 joules

Explanation:

The work done on an object is equal to its change in kinetic energy: Change in KE = F × d.

Plug the values for F and d into the formula and solve:

Change in KE = 2,524 × 180

= 454,320 joules

The roller coaster gains 454,320 joules of energy from the work done on it by the chain.

7 0

3 years ago

Read 2 more answers

Consider a particle with unit charge q, and mass m, in a constant magnetic field B directed along the positive z–axis. The parti

max2010maxim [7]

Answer:

it must be helical motion in which the charge particle will move uniformly along z axis and simultaneously it will move in circular path in xy plane.

Explanation:

Magnetic field is along z axis while velocity is in x-z plane

so we will have

$F = q(\vec v \times \vec B)$

so here we can say

$F = q(u\hat i + w\hat k) \times (B \hat k)$

so we will have

$F = quB(-\hat j)$

so here the net force on the charge is perpendicular to its x directional velocity along - Y direction

So due to this component of motion it will move along a circle while other component of the motion will remain uniform always

So here it is combination of two parts

1) Uniform circular motion

2) Uniform motion

So we can say that it must be helical motion in which the charge particle will move uniformly along z axis and simultaneously it will move in circular path in xy plane.

4 0

2 years ago