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Amiraneli [1.4K]

3 years ago

11

Which label identifies the statement: "Energy cannot be created or destroyed, but it can be converted or changed into different

forms. A. the law of energy transformation B. the law of conservation of matter C. the law of energy equilibrium D. the law of conservation of energy

1 answer:

podryga [215]3 years ago

7 0

D. The law of conservation of energy identifies the statement

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When light reaches a barrier or the edge of an opening it diffracts, which means that the light _________. A) bends. B) bounces

rusak2 [61]

A. it bends when light reaches an end of a barrier it will bend.

3 0

3 years ago

Read 2 more answers

2.) The lob in tennis is an effective tactic when your opponent is near the net. It consists of lofting the ball over his/her he

Ratling [72]

Answer:

The minimum average speed the opponent must move so that he is in position to hit the ball is approximately 5.79 m/s

Explanation:

The given parameters of the ball are;

The initial speed of the ball = 15 m/s

The direction in which the ball is launched = 50° above the horizontal

The location of the other tennis player when the ball is launched = 10 m from the ball

The time at which the other tennis player begins to run = 0.3 seconds after the ball is launched

The height at which the ball is hit back = 2.1 m above the height from which the ball is launched

The vertical position, 'y', at time, 't', of a projectile motion is given as follows;

y = (u·sinθ)·t - 1/2·g·t²

When y = 2.1 m, we have;

2.1 = (15·sin(50°))·t - 1/2·9.8·t²

∴ 4.9·t² - (15·sin(50°))·t + 2.1 = 0

Solving with the aid of a graphing calculator function, we get;

t = 0.199776187257 s or t = 2.14525782198 s

Therefore, the ball is at 2.1 m above the start point on the other side of the court at t ≈ 2.145 seconds

The horizontal distance, 'x', the ball travels at t ≈ 2.145 seconds is given as follows;

x = u × cos(50°) × t = 15 × cos(50°) × 2.145 ≈ 20.682 m

The horizontal distance the ball travels at t ≈ 2.145 seconds, x ≈ 20.682 m

Therefore, we have;

The time the other player has to reach the ball, t₂ =2.145 s - 0.3 s ≈ 1.845 s

The distance the other player has to run, d = 20.682 m - 10 m = 10.682 m

The minimum average speed the other player has to move with, $v_s$ = d/t₂

∴ $v_s$ = 10.682 m/(1.845 s) ≈ 5.78970189702 m/s ≈ 5.79 m/s

The minimum average speed the opponent must move so that he is in position to hit the ball, $v_s$ ≈ 5.79 m/s.

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3 years ago

If the potential difference across a 12-ohm resistor is 6 volts, the current through the resistor is?

larisa86 [58]

Current is inversely proportional to the resistance of the resistor and directly to the potential difference across it.

I = V/R = 6/12 = 0.5 A

4 0

3 years ago

Which is not an example of a scalar?

Crank

Answer:

b) 2ft/s

Explanation:

A scalar has only magintude, not direction

6.2m, 3kg, and -100 o C are all scalars because they only have magnitude.

2ft/s is not a scalar because it has a direction.

3 0

2 years ago

A Red Rider bb gun uses the energy in a compressed spring to provide the kinetic energy for propelling a small pellet of mass 0.

Kay [80]

Answer:

a.6.5025 J

b.6.5025 J

Explanation:

We are given that

Mass of pellet,m=0.27 g= $0.27\times 10^{-3} kg$

1 kg=1000 g

Spring constant,k=1800 N/m

x=8.5 cm= $8.5\times 10^{-2} m$

1m=100 cm

a.Potential energy stored in the compressed spring is given by

P.E= $\frac{1}{2}kx^2$

$P.E=\frac{1}{2}(1800)(8.5\times 10^{-2})^2$

$P.E=6.5025 J$

b.By using law of conservation of energy

P.E of spring=K.E of the pellet

K.E of the pellet=6.5025 J

6 0

3 years ago