A boy is pulling a box on the ground by a string to the right. What four forces he using?

A ball is thrown vertically upward with a

Veronika [31]

Answer:

1) The maximum height reached is approximately 39.715 m

2) The time it takes the ball to reach the its highest point is approximately 2.85 s

Explanation:

1) The vertical velocity of the ball, u = 27.9 m/s

The acceleration due gravity, g = 9.8 m/s²

The kinematic equation that gives the height, h, reached by the ball is given as follows;

v² = u² - 2·g·h

Where;

v = The final velocity of the ball = 0 m/s at the maximum height

h = The height reached by the ball = $h_{max}$ at maximum height

Therefore, by substitution of the known values, we have;

v² = u² - 2·g·h

0² = 27.9² - 2 × 9.8 × $h_{max}$

2 × 9.8 × $h_{max}$ = 27.9²

$h_{max}$ = 27.9²/(2×9.8) ≈ 39.715

The maximum height reached = $h_{max}$ ≈ 39.715 m

2) From the kinematic equation of motion, v = u - g·t, we have the time, t, it takes the ball to reach the maximum height given as follows

At maximum height, the final velocity, v = 0 m/s, therefore, we have;

0 = 27.9 - 9.8 × t

9.8 × t = 27.9

t = 27.9/9.8 ≈ 2.85

The time it takes the ball to reach the maximum height = t ≈ 2.85 seconds.

6 0

3 years ago

What test were used to find out information about the iceman

Blababa [14]

To find information, the would take DNA tests.

6 0

3 years ago

Science fiction movies that include explosion sound effects for battles in space are not scientifically correct. Why is this?

Reil [10]

B. There is not enough matter in space to transmit sound waves.

Explanation:

Sound waves are created when there is a vibration of the particles in a medium. For example, our voice is an example of sound wave: when we speak, the molecules of air around us start vibrating, producing regions of higher concentration of molecules (called compressions) and of lower concentration (called rarefactions). It is clear from this definition that sound waves can only propagate if there is a physical medium: such as a gas, a liquid or a solid, but sound waves cannot propagate through empty space.

Since space is almost empty, the correct choice is

B. There is not enough matter in space to transmit sound waves.

6 0

3 years ago

The activation energy of a reaction going on its own is 20 kj. If the reaction was treated with a catalyst, which would most lik

storchak [24]

Answer:

15 kJ

Explanation:

We need to know the following;

what is activation energy?

Activation energy is the minimum energy required by reactants for a chemical reaction to take place.

What are catalysts?

Catalysts are molecules or substances that speed up the rate of a chemical reaction.

In other words, catalysts increase the speed at which products are formed from reactants.

How do catalysts speed up reactions?

Catalysts speed the rate of chemical reactions by lowering the activation energy of the reactants.
When activation energy is lowered, reactants require less energy for the reaction to occur which easily achieved making the reaction proceed faster.
Therefore, in presence of a catalyst, the new activation energy should be lower than the initial value of activation energy.

7 0

3 years ago

Read 2 more answers

A speeding car is pulling away from a police car. The police car is moving at 30 m/s. The radar gun in the police car emits an e

Gekata [30.6K]

Answer:

65.625 m/s

Explanation:

$F=20\times 10^9 Hz$