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3 years ago

Which of the following statements accurately describes the sign of the work done on the box by the force of the push?

Physics

1 answer:

USPshnik [31]3 years ago

4 0

Answer: positive

Explanation: according to newton's second law of motion, the applied force (pull) will produce a motion for the box defined by the formulae

f = ma, where m is the mass of the box and a is the acceleration.

But due to friction, a force of the same magnitude but opposite in direction to the push is applied, hence we have that

f - fr = ma

Where fr is the frictional force.

As we can see from the formulae, f (push) is responsible for a positive work while fr (friction) will bring about a negative work done.

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A ball is swung in a horizontal circle at a constant speed. Each circle takes 0.85 seconds to complete and the rope is 0.40 m lo

BaLLatris [955]

Answer:

The centripetal acceleration will be "21.785 m/s²".

Explanation:

The given values are:

Time,

t = 0.85 seconds

Length of rope,

r = 0.40 m

Mass of ball,

m = 0.80 kg

As we know,

⇒ $w=\frac{2 \pi}{t}$

On substituting the values, we get

⇒ $=\frac{2\times 3.14}{0.85}$

⇒ $= \frac{6.28}{0.85}$

⇒ $=7.38 \ rad/s^2$

The centripetal acceleration will be:

⇒ $a=r\times w^2$

⇒ $=0.40\times (7.38)^2$

⇒ $=0.40\times 54.46$

⇒ $=21.785 \ m/s^2$

7 0

2 years ago

A runner runs 300 m at an average speed of 3.0 m/s. She then runs another 300m at an average

Kaylis [27]

Answer:

B. 4 m/s

Explanation:

v=d/t

Running for 300 m at 3 m/s takes 100 seconds and running at 300 m at 6 m/s takes 50 seconds. 100 s + 50 s = 150 s (total time). Total distance is 600 m, so 600 m/ 150 s = 4 m/s.

3 0

3 years ago

You drop a stone down off a bridge. You are able to count to 4.0 seconds when it finally hits the water. How high is the bridge?

mart [117]

Answer:

The height of the bridge is 78.4 m.

Explanation:

Given;

time of the stone motion off the bridge, t = 4.0 s

acceleration due to gravity, g = 9.8 m/s²

The height of the bridge is given by;

h = ut + ¹/₂gt²

where;

u is the initial velocity of the stone, u = 0

h = ¹/₂gt²

h = ¹/₂(9.8)(4)²

h = 78.4 m

Therefore, the height of the bridge is 78.4 m.

7 0

2 years ago

If a bust starts to move and its velocity becomes 90 km after 8 seconds . calculate its acceleration answer it quick please

kherson [118]

Answer:

a = 3.125 [m/s^2]

Explanation:

In order to solve this problem, we must use the following equation of kinematics. But first, we have to convert the speed of 90 [km/h] to meters per second.

$90\frac{km}{h}*\frac{1000m}{1km}*\frac{1h}{3600s} \\= 25 \frac{m}{s}$

$v_{f} =v_{i} + (a*t)$

where:

Vf = final velocity = 25 [m/s]

Vi = initial velocity = 0

a = acceleration [m/s^2]

t = time = 8 [s]

The initial speed is zero as the bus starts to koverse from rest. The positive sign of the equation means that the bus increases its speed.

25 = 0 + a*8

a = 3.125 [m/s^2]

3 0

2 years ago

Why does it takes the outer planets so long to orbit the Sun? Try to come up with two reasons.

tensa zangetsu [6.8K]

well they are normally bigger than the inner planets, and they also have a bigger distance to go

7 0

3 years ago