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3 years ago

A 4 kg bowling ball rolls at a speed of 5 m/s on the roof of a building that is 30 meters tall. What is its kinetic energy?

Physics

1 answer:

klasskru [66]3 years ago

3 0

ans: B

Kinetic energy = $\frac{1}{2} mv^{2}$

= $\frac{1}{2} (4)(5^{2} )$

= 50J

ps. the height will only affect its potential energy, not kinetic.

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A block of weight 45.7 N is hanging from a rope. The tension from the rope is pulling upward on the block. The block is accelera

viktelen [127]

<h2>Answer:</h2><h2></h2>

52.555 N

<h2>Explanation:</h2>

Let's use Newton's second law of motion here which states that the resultant force (∑F) acting on a body is the product of the mass (m) of the body and the acceleration (a) due to this force. i.e

∑F = m x a ---------------------(i)

<em>Now, let's get the resultant force;</em>

Two main forces are acting on the rope;

i. the weight (W) of the block acting downwards.

Where;

W = mass of block(m) x gravity(g) = m x g

ii. the tension (T) in the rope acting upwards.

Therefore, the resultant force is the vector sum of these two forces as follows;

∑F = - W + T [upward motion is taken as positive. hence -W and +T]

<em>Substitute ∑F = - W + T into equation (i) as follows;</em>

- W + T = m x a ---------------------(ii)

<em>From the question;</em>

* Weight (W) of the block = 45.7N

=> mass (m) of the block = W / g = 45.7 / 10 [Taking g = 10m/s²]

=> m = 4.57 kg

* acceleration (a) = 1.50m/s²

<em>Substitute these values into equation (ii) as follows;</em>

- 45.7 + T = 4.57 x 1.50

- 45.7 + T = 6.855

<em>Solve for T;</em>

T = 6.855 + 45.7

T = 52.555 N

Therefore, the tension in the rope is 52.555 N

6 0

4 years ago

Scientists on Earth are able to communicate with rovers on Mars through their receivers, which can receive and process signals.

Bas_tet [7]

B electromagnetic waves I think

4 0

3 years ago

Read 2 more answers

5. Which of these affect the brightness of a bulb? Choose all that apply.* 6 po

schepotkina [342]

Answer:

The voltage of the battery

7 0

3 years ago

How much heat is released when 432 g of water cools down from 71'c to 18'c?

maria [59]

The heat released by the water when it cools down by a temperature difference $\Delta T$ is
$Q=mC_s \Delta T$
where
m=432 g is the mass of the water
$C_s = 4.18 J/g^{\circ}C$ is the specific heat capacity of water
$\Delta T =71^{\circ}C-18^{\circ}C=53^{\circ}$ is the decrease of temperature of the water

Plugging the numbers into the equation, we find
$Q=(432 g)(4.18 J/g^{\circ}C)(53^{\circ}C)=9.57 \cdot 10^4 J$
and this is the amount of heat released by the water.

7 0

3 years ago

A 12.0-kg block is pushed across a rough horizontal surface by a force that is angled 30.0◦ below the horizontal. The magnitude

Juli2301 [7.4K]

Answer:

157.36 N

Explanation:

Contact force is the force which is created due to contact and it is applied on the contact point . The force applied by body on the surface is its weight .

If R be the reaction force of the ground

R = mg + F son30

= 12 x 9.8 + 75 sin 30

= 117.6 + 37.5

= 155.10 N .

friction force = f

Net force in forward direction = F cos 30 - f = ma

75cos 30 - f = 12 x 3.2

f = 65 - 38.4

= 26.6 N

Total force on the surface =√( f² + R² )

√ (26.6² + 155.1²)

= √707.56 + 24056²

=√ 24763.57

= 157.36 N.

contact force = 157.36 N .

6 0

3 years ago