When an object gains kinetic energy, is the work done the object postive, negative, or zero?

What is characteristic of both sound waves andelectromagnetic waves?(1) They require a medium.(2) They transfer energy.(3) They

Amiraneli [1.4K]

The correct answer would be 2: they transfer energy.

3 0

3 years ago

The automobile has a weight of 2700 lb and is traveling forward at 4 ft>s when it crashes into the wall. If the impact occurs

alex41 [277]

Answer:

$F_b=153918\, lb.ft.s^{-2}$

Explanation:

Given:

mass, $m=2700 \,lb$

time, $t=0.06\,s$

velocity, $v=4\,ft.s^{-1}$

coefficient of kinetic friction between wheels & pavement, $\mu=0.3$

According to first condition,

$F\times \Delta t=m\times v$

$F\times 0.06= 2700\times 4$

$F=180000\,lb.ft.s^{-2}$

According to second condition,

Magnitude of frictional force (which acts opposite to the direction of motion):

$f=\mu.N$

where N is the normal reaction.

$f=0.3\times 2700\times 32.2$

$f=26082 \,lb.ft.s^{-2}$

Now, the impulsive force on the wall if the brakes were applied during the crash:

$F_b= F-f$

$F_b=180000-26082$

$F_b=153918\, lb.ft.s^{-2}$

3 0

4 years ago

Two blocks in contact with each other are pushed to the right across a rough horizontal surface by the two forces shown. If the

ale4655 [162]

I assume the blocks are pushed together at constant speed, and it's not so important but I'll also assume it's the smaller block being pushed up against the larger one. (The opposite arrangement works out much the same way.)

Consider the forces acting on either block. Let the direction in which the blocks are being pushed by the positive direction.

The 2.0-kg block feels

• the downward pull of its own weight, (2.0 kg) g

• the upward normal force of the surface, magnitude n₁

• kinetic friction, mag. f₁ = 0.30n₁, pointing in the negative horizontal direction

• the contact force of the larger block, mag. c₁, also pointing in the negative horizontal direction

• the applied force, mag. F, pointing in the positive horizontal direction

Meanwhile the 3.0-kg block feels

• its own weight, (3.0 kg) g, pointing downward

• normal force, mag. n₂, pointing upward

• kinetic friction, mag. f₂ = 0.30n₂, pointing in the negative horizontal direction

• contact force from the smaller block, mag. c₂, pointing in the positive horizontal direction (this is the force that is causing the larger block to move)

Notice the contact forces form an action-reaction pair, so that c₁ = c₂, so we only need to find one of these, and we can get it right away from the net forces acting on the 3.0-kg block in the vertical and horizontal directions:

• net vertical force:

n₂ - (3.0 kg) g = 0 ==> n₂ = (3.0 kg) g ==> f₂ = 0.30 (3.0 kg) g

• net horizontal force:

c₂ - f₂ = 0 ==> c₂ = 0.30 (3.0 kg) g ≈ 8.8 N

4 0

3 years ago

This position-time graph describes an object's motion. Use it to determine the

kirza4 [7]

We're happy that you're asking for the "displacement", because displacement is simply the straight-line distance between the start-point and end-point, and we don't care about any of the motions or gyrations along the way.

From the graph:

-- The location of the object at time-zero, when time begins, is 10 meters.

-- The location of the object after 6.0 seconds is 4 meters.

-- The distance between the start-point and end-point is

(final location) - (initial location)

-- So Displacement = (4 meters) - (10 meters)

Displacement = -6 meters

3 0

3 years ago

If you hike up Eagle Mountain to its peak (highest elevation), what side would be easiest to climb up: East or West? How do you

mihalych1998 [28]

because I googled it and are you going there or something

6 0

4 years ago