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N76 [4]
3 years ago
7

The objective lens in a DVD player must move quickly to keep the laser beam focused on the disc's reflective layer. Why must thi

s lens have a very small mass?
Physics
1 answer:
Zinaida [17]3 years ago
4 0

Explanation:

The small mass of lens in a DVD player accounts for small inertia of the lens. Hence, even on application of force of small magnitude, the lens is rapidly accelerated. Moreover, the small mass of lens also accounts for lower resistance to change in its motion and therefore, again can be rapidly accelerated back and forth.

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What happens when the thermal energy of a substance increases?
Sonja [21]

When thermal energy of a substance increases, it's entropy(randomness) & Kinetic energy increases.

For more appropriate answer, you should put the options 'cause there could be more than one answer for this question.

4 0
3 years ago
If you wanted to soundproof a room what insulator would you use
olasank [31]

Answer:

foam but thats what i heard from other people

Explanation:

4 0
3 years ago
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A 40W lamp wastes 34 J of energy every second by heating its surroundings.
Artemon [7]

Answer:

15\%.

Explanation:

The efficiency of a machine is the percentage of energy input that was turned into useful energy.

The power rating of this lamp is 40\; \rm W (same as 40\; \rm J \cdot s^{-1},) meaning that 40\; \rm J of energy is supplied to this lamp every second.

The question states that 34\; \rm J out of that 40\; \rm J of energy input would be turned into heat, which is not useful energy output in this scenario. Assuming that all other forms of energy loss is negligible. The rest of the (40\; \rm J - 34\; \rm J) = 6\; \rm J of energy supplied to this lamp would be turned into useful energy output.

Thus, every second, this lamp would receive 40\; \rm J of energy input and would outputs 6\; \rm J of useful work. The efficiency of this lamp would be:

\begin{aligned}& \text{Efficiency} \\ =\; & \frac{\text{Useful energy out}}{\text{Total energy in}} \times 100\% \\ =\; & \frac{6\; \rm J}{40\; \rm J} \times 100\%\\ =\; &15\% \end{aligned}.

4 0
2 years ago
Can anyone help me with this please​
Anastasy [175]

Answer:

1270 J

Explanation:

Recall that the mechanical energy of a system is the addition of the Potential energy and the Kinetic energy at any given time.

As the skier descends, potential energy is converted into kinetic energy, but the total mechanical energy should remain the same.

We see that it is not the case, so that difference is what has gone into thermal energy;  19500 J - 18230 J = 1270 J

7 0
3 years ago
What is the acceleration of a boy on a skateboard if the net force on the boy is 15 N? The total mass of the boy and the skatebo
Stels [109]
                                 Force = (mass) x (acceleration)

If the full 15N is pointing parallel to the ground,
then

                                   15 N  =  (58 kg) x (acceleration).

Divide each side
by  58 kg:                   Acceleration = 15 N / 58 kg

                                                         = (15 kg-m/s²) / (58 kg)

                                                         = (15/58) (kg-m/kg-s²)

                                                         =  0.26 m/s² .
7 0
3 years ago
Read 2 more answers
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