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Hitman42 [59]
3 years ago
8

Sam stands on a 20 m high cliff and throws a 45 g rock with an initial velocity of 5 m/s [forward] to the water below. Use the c

onservation of energy to determine the speed of the rock when it has fallen 12 m.
Physics
1 answer:
storchak [24]3 years ago
5 0

Answer:

v = 12.52 [m/s]

Explanation:

To solve this problem we must use the energy conservation theorem. Which tells us that potential energy is transformed into kinetic energy or vice versa. This is more clearly as the potential energy decreases the kinetic energy increases.

Ep = Ek

where:

Ep = potential energy [J] (units of joules]

Ek = kinetic energy [J]

Ep = m*g*h

where:

m = mass of the rock = 45 [g] = 0.045 [kg]

g = gravity acceleration = 9.81 [m/s²]

h = elevation = (20 - 12) = 8 [m]

Ek = 0.5*m*v²

where:

v = velocity [m/s]

The reference level of potential energy is taken as the ground level, at this level the potential energy is zero, i.e. all potential energy has been transformed into kinetic energy. In such a way that when the Rock has fallen 12 [m] it is located 8 [m] from the ground level.

m*g*h = 0.5*m*v²

v² = (g*h)/0.5

v = √(9.81*8)/0.5

v = 12.52 [m/s]

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Ksivusya [100]

if there is not a reaction


5 0
3 years ago
Runner A is initially 6.0 km west of a flagpole and is running with a constant velocity of 9.0 km/h due east. Runner B is initia
sergejj [24]

Answer:

0.176m from the flagpole, westward.

Explanation:

Let the Eastward be the positive direction. So initially runner A is at position -6km, running with velocity of 9km/h while runner B is at position 5km running at a velocity of -8km/h. We can conduct the following equation for their distances over the same time t

s_A = -6 + 9t

s_B = 5 - 8t

When A an B meets, they are at the same position and at the same time. So

s_A = s_B

-6 +9t = 5 - 8t

17t = 5 + 6 = 11

t = 11/17 = 0.647 s

s_A = -6 + 9*0.647 = -0.176 m

So where they meet is 0.176m from the flagpole, westward.

5 0
3 years ago
What is the force of gravity between two 40.0kg masses that are separated by 3.00m?
Slav-nsk [51]

Answer:

f = g \times \frac{m1 \times m2}{ {d}^{2} }

f = 6.67 \times  {10}^{ - 11}  \times \frac{40 \times 40}{9}

<h2>F=1.2x 10^-8</h2>
3 0
3 years ago
You are driving to the grocery store at 18 m/sm/s. You are 160 mm from an intersection when the traffic light turns red. Assume
inysia [295]

Answer:

part(a) 151 m

part(b) 1.073 m/s2

part(c) 16.7 secs

Explanation:Firstly the person applied brakes 0.5 secs after seeing the red light hence the distance traveled during this time is

d=v*t

d=18*0.5

d=9m

For part (a)

I have corrected this question and now

The person was 160m from the intersection before applying the brakes as he traveled 9m before the brakes

He is now 151 m from intersection as

s=160-9

s= 151 m

part (b)

As it is given that velocity of the car is 0 at the intersection so we use this information in kinematic equation

v^2=u^2+2as

here u=18m/s and s=151

0=18^2+2a*151\\302a=-324\\a=-1.073 m/s^2

To calculate time we can use the acceleration equation

a=\frac{v-u}{t} \\t=\frac{v-u}{a}\\t=18/1.073\\t=16.77 secs

6 0
3 years ago
A 523.2-W space heater is designed for operation in Germany, where household electrical outlets supply 230 V (rms) service. What
photoshop1234 [79]

Answer:

power = 142.4 W

Explanation:

power of heater in Germany (P₁) = 523.2 W

power of heater in America (P₂) = ?

outlet voltage in Germany (V₁) = 230 V

outlet voltage in America (V₂) = 120 V

  • While in Germany, power = \frac{V₁^{2}}{R}

         523.2 = \frac{230^{2}}{R}

         R = 101.1

  • While in America, also power = \frac{V₂^{2}}{R}

         using the value of R gotten above

         power = \frac{120^{2}}{101.1}

        power = 142.4 W

6 0
3 years ago
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