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2 years ago

15

a powerboat accelerates along a straight path from 0 km/hr to 99.8 km/hr in 10.0 s.Find the average acceleration of the boat in

meters per second squared.

1 answer:

Alex777 [14]2 years ago

3 0

(27.72-0)/10
= 2.772 m/s2

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What is the minimum amount of energy required to completely melt a 7.25-kg lead brick which has a starting temperature of 18.0 °

Delvig [45]

Answer: c. 4.56 × 105 J

Explanation:

Given that

mass of lead brick, m= 7.25kg

Temperature T1 = 18.0 °C

Temperature T2 = 328 °C

specific heat capacity of lead, c = 128 J/(kg∙C°)

latent heat of fusion Lfusion =23,200 J/kg

Amount of energy Q =?

Using the formulae

Amount of energy ,Q =mc ( T2-T1)+ mLfusion

7.25kg x 128 J/(kg∙C°) x (328-18°C) + 7.25kg x 23200 J/kg

=455880J

=4.56 x 10^5 J

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2 years ago

The electric field at a point 2.8 cm from a small object points toward the object with a strength of 180,000 N/C. What is the ob

givi [52]

Answer:

Charge, $Q=1.56\times 10^{-8}\ C$

Explanation:

It is given that,

Electric field strength, E = 180000 N/C

Distance from a small object, r = 2.8 cm = 0.028 m

Electric field at a point is given by :

$E=\dfrac{kQ}{r^2}$

Q is the charge on an object

$Q=\dfrac{Er^2}{k}$

$Q=\dfrac{180000\ N/C\times (0.028\ m)^2}{9\times 10^9\ Nm^2/C^2}$

$Q=1.56\times 10^{-8}\ C$

So, the charge on the object is $1.56\times 10^{-8}\ C$ . Hence, this is the required solution.

7 0

2 years ago

Ever tried to stop a 150-pound (68 kg) cannonball fired towards you at 30 mph (48 km/hr.)? No, probably not. But you may have tr

alex41 [277]

The two situations are similar because in both you are trying to minimize the damage and make the best out of a bad situation

8 0

2 years ago

You are driving to the grocery store at 20 m/s. You are 110m from an intersection when the traffic light turns red. Assume that

oksano4ka [1.4K]

As we know that reaction time will be

$t = 0.50 s$

so the distance moved by car in reaction time

$d = vt$

$d = 20 \times 0.50$

$d = 10 m$

now the distance remain after that from intersection point is given by

$d = 110 - 10 = 100 m$

So our distance from the intersection will be 100 m when we apply brakes

now this distance should be covered till the car will stop

so here we will have

$v_f = 0$

$v_i = 20 m/s$

now from kinematics equation we will have

$v_f^2 - v_i^2 = 2 a d$

$0 - 20^2 = 2(a)100$

$a = \frac{-400}{200} = -2 m/s^2$

so the acceleration required by brakes is -2 m/s/s

Now total time taken to stop the car after applying brakes will be given as

$v_f - v_i = at$

$0 - 20 = -2 (t)$

$t = 10 s$

total time to stop the car is given as

$T = 10 s + 0.5 s = 10.5 s$

3 0

2 years ago

An 888.0 kg elevator is moving downward with a velocity of 0.800 m/s. It decelerates uniformly and comes to a stop in a distance

bagirrra123 [75]

Answer:

The value of tension on the cable T = 1065.6 N

Explanation:

Mass = 888 kg

Initial velocity ( u )= 0.8 $\frac{m}{sec}$

Final velocity ( V ) = 0

Distance traveled before come to rest = 0.2667 m

Now use third law of motion $V^{2}$ = $u^{2}$ - 2 a s

Put all the values in above formula we get,

⇒ 0 = $0.8^{2}$ - 2 × a ×0.2667

⇒ a = 1.2 $\frac{m}{sec^{2} }$

This is the deceleration of the box.

Tension in the cable is given by T = F = m × a

Put all the values in above formula we get,

T = 888 × 1.2

T = 1065.6 N

This is the value of tension on the cable.

5 0

2 years ago