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valentina_108 [34]
3 years ago
8

A 1.8 kg book had been dropped from the top of the football stadium. It's speed is 4.8 m/s when it is 2.9 meters above the groun

d what is its mechanical energy?
Physics
1 answer:
MrRissso [65]3 years ago
4 0

Answer:

72.936 Joule

Explanation:

Mechanical Energy = Potential Energy + Kinetic Energy

Kinetic Energy = (1/2) x m x V² = (1/2) x 1.8 x 4.8² = 20.736 J

Potential Energy = m x g x h = 1.8 x 10 x 2.9 = 52.2 J

Total Mechanical Energy = 20.736 + 52.2 = 72.936 Joule

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While running at a constant velocity, how should you throw a ball with respect to you so that you can catch it yourself?
timurjin [86]
You are running at constant velocity in the x direction, and based on the 2D definition of projectile motion, Vx=Vxo. In other words, your velocity in the x direction is equal to the starting velocity in the x direction. Let's say the total distance in the x direction that you run to catch your own ball is D (assuming you have actual values for Vx and D). You can then use the range equation, D= (2VoxVoy)/g, to find the initial y velocity, Voy. g is gravitational acceleration, -9.8m/s^2. Now you know how far to run (D), where you will catch the ball (xo+D), and the initial x and y velocities you should be throwing the ball at, but to find the initial velocity vector itself (x and y are only the components), you use the pythagorean theorem to solve for the hypotenuse. Because you know all three sides of the triangle, you can also solve for the angle you should throw the ball at, as that is simply arctan(y/x). 
5 0
3 years ago
1. A baseball is thrown vertically at 16.7 m/s. What is the maimum height of the baseball?
Anvisha [2.4K]

Answer:

14.2 m

Explanation:

Using conservation of energy:

PE at top = KE at bottom

mgh = ½ mv²

h = v² / (2g)

h = (16.7 m/s)² / (2 × 9.8 m/s²)

h = 14.2 m

Using kinematics:

Given:

v₀ = 16.7 m/s

v = 0 m/s

a = -9.8 m/s²

Find: Δy

v² = v₀² + 2aΔy

(0 m/s)² = (16.7 m/s)² + 2 (-9.8 m/s²) Δy

Δy = 14.2 m

7 0
3 years ago
A 60-kg rollerblader rolls 10 m down a 30? incline. When she reaches the level floor at the bottom, she applies the brakes. The
VARVARA [1.3K]

Answer:

s = 20 m

Explanation:

given,

mass of the roller blader = 60 Kg

length = 10 m

inclines at = 30°

coefficient of friction = 0.25

using conservation of energy

\dfrac{1}{2}mu^2 = m g d sin \theta

u^2 = 2 g d sin30^0

u= \sqrt{2\times 9.8 \times 10 sin30^0}

u = 9.89 m/s

Using second law of motion  

ma =μ mg

a = μ g

a = 0.25 x 9.8

a = 2.45 m/s²

Using third equation of motion ,  

v² - u² = 2 a s

0² - 9.89² = 2 x 2.45 x s

s = 20 m

the distance moved before stopping is 20 m

3 0
3 years ago
The length of a 100 mm bar of metal increases by 0.3 mm when subjected to a temperature rise of 100°C. The coefficient of linear
Juli2301 [7.4K]

Answer:

α = 3×10^-5 K^-1

Explanation:

let ΔL be the change in length of the bar of metal, ΔT be the change in temperature, L be the original length of the metal bar and let α be the coefficient of linear expansion.

then, the coefficient of linear expansion is given by:

α = ΔL/(ΔT×L)

   = (0.3×10^-3)/(100)(100×10^-3)

   = 3×10^-5 K^-1

Therefore, the coefficient of linear expansion is 3×10^-5 K^-1

5 0
3 years ago
If the angle of refraction is 20 degrees what is the angle of incidence​
Romashka-Z-Leto [24]

Answer:

13.1

Explanation:

that's what I'm gonna go with, but u can research more

5 0
3 years ago
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