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lisov135 [29]
3 years ago
7

An athlete kicks a soccer ball that starts at rest so that it leaves their foot with a speed of 10m/s from the top o f a rectang

ular shaped canyon. If the athlete's foot is in contact with the ball for only 0.02 seconds, determine the accceleration of the ball during the kick.
Physics
1 answer:
kirza4 [7]3 years ago
3 0

Answer:

a=500m/s^2

Explanation:

We need only to apply the definition of acceleration, which is:

a=\frac{v_f-v_i}{t_f-t_i}

In our case the final velocity is v_f=10m/s, the initial velocity is v_i=0m/s since it departs from rest, the final time is t_f=0.02s and the initial time we are considering is t_i=0s

So for our values we have:

a=\frac{10m/s-0m/s}{0.02s-0s}=500m/s^2

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A robot that can move a hand left and right and rotate the hand 360º is said to have
Luda [366]

You've described two (2) axes of motion.
The third one would have been up-and-down.
 
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2 years ago
A gray kangaroo can bound across level ground with each jump carrying it 8.7 from the takeoff point. Typically the kangaroo leav
oksano4ka [1.4K]

Answer:

a) The takeoff speed is 10 m/s.

b) The maximum height above the ground is 1.2 m.

Explanation:

The position of the kangaroo and its velocity at any given time "t" can be calculated by the following equations:

r = (x0 + v0 · t · cos α, y0 + v0 · t · sin α + 1/2 · g · t²)

v =(v0 · cos α, v0 · sin α + g · t)

Where:

r = position vector at time "t".

x0 = initial horizontal position.

v0 = initial velocity.

α = jumping angle.

y0 = initial vertical position.

g = acceleration due to gravity (-9.8 m/s² considering the upward direction as positive).

v = velocity vector at time "t"

a) Please see the attached figure for a better understanding of the problem. In red is depicted the position vector at the final time (r final). The components of r final are known:

r final = (8.7 m, 0 m)

Then at final time:

8.7 m = x0 + v0 · t · cos α

0 m = y0 + v0 · t · sin α + 1/2 · g · t²

(notice in the figure that the origin of the frame of reference is located at the jumping point so that x0 and y0 = 0). Then:

8.7 m = v0 · t · cos α

Solving for "v0":

8.7 m /(t · cos α) = v0

Replacing v0 in the equation of the y-component, we can obtain the final time:

0 m = 8.7 m · tan 29° - 1/2 · 9.8 m/s² · t² (remember: sin α / cos α = tan α)

- 8.7 m · tan 29° / -4.9 m/s² = t²

t = 0.99 s

Now, we can calculate the initial speed:

8.7 m /t · cos α = v0

v0 = 8.7 m / (0.99 s · cos 29°)

<u>v0 = 10 m/s</u>

The takeoff speed is 10 m/s

b) When the kangaroo is at its maximum height, the velocity vector is horizontal (see figure). That means that the y-component of the velocity at that time is 0:

0 = v0 · sin α + g · t

Solving for "t":

-v0 · sin α / g = t

t = - 10 m/s · sin 29° / 9.8 m/s²

t = 0.49 s

Notice that we could have halved the final time (0.99 s, calculated above) to obtain the time at which the kangaroo is at its maximum height. That´s because the trajectory is parabolic.

Now, let´s find the height of the kangaroo at that time:

y = y0 + v0 · t · sin α + 1/2 · g · t²

y = 10 m/s · 0.49 s · sin 29° - 1/2 · 9.8 m/s² · (0.49 s)²

<u>y = 1.2 m</u>

The maximum height above the ground is 1.2 m.

4 0
3 years ago
NEED HELP PLEASE 15 POINTS PLEASEE NEED HELP
Ostrovityanka [42]

Answer:

I wish I knew

Explanation:

5 0
3 years ago
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Why is there no effect on other branches in a paral- lel circuit when one branch of the circuit is opened or closed?
motikmotik

Answer:

Explanation:

As the circuit is parallel, then there is no effect of other branches as the potential difference across each arm is same.

6 0
3 years ago
Henry slides across an icy pond. The coefficient of kinetic friction betweenhis shoes and the ice is 0.09. If his mass is 115 kg
Kruka [31]

Answer:

101 N

Explanation:

4 0
2 years ago
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