# Physics

posted by .

A ball moves at 33m/s through a wall of donuts 31 cm thick. It comesout of the donut wall at 18 m/s. How much time does it spend in the wall of donuts? How thick would the wall of dounts need to be to stop the ball entirely?

Is the answer 1.3 secondsand the wall would need to be 27 cm thick?

• Physics -

The average velocity in the donuts is

(33+18)/2 or 25.5m/s

avgvelocity=distance/time
you know avgvelocity, and distance, solve for time.

I don't get your time.

Now, for the thickness. find the acceleration of the ball in the donuts
Vf^2=Vi^2 + 2ad (solve for a)
now use the same equation with that a to solve for d if Vf is zero.

• Physics -

Assuming uniform deceleration, which may not be valid, the average speed going through is 25.5 m/s and the time is 0.31 m/25.5 m/s = 0.012 s

You are quite far off. Did you forget to express the wall thickness in meters?

Your last answer is also incorrect. If the ball goes through 31 cm that quickly, while losing less than half its speed, why would a thinnner wall stop it?

Assume speed reduction is proportional to thickness.
15/33 = 31/x

x is the required thickness

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### Physics

A rubber ball is thrown against the wall. The ball has a mass of 4 g and strikes the wall perpendicularly with a speed of 12 m/s. The acceleration is constant while the ball is touching the wall. After touching the wall, the center …
2. ### Physics

Consider 3 layers of a wall. The first layer is plaster 1.0 cm thick(R=0.033 SI units), the second layer is fiberglass insulation 8.9 cm thick (r=2.97), and the outside layer is woodd 3.0 cm thick(0.33). What is the heat loss through …
3. ### physics

Consider three layers of a wall. The first layer is plaster 1.0 cm thick (R = 0.033 SI units), the second layer is fiberglass insulation 8.9 cm thick (R = 2.97), and the outside layer is wood 3.0 cm thick (R = 0.33). What is the heat …
4. ### physics

A 3.56-kg steel ball strikes a massive wall at 10.0 m/s at an angle of θ = 60.0° with the plane of the wall. It bounces off the wall with the same speed and angle (see the figure below). If the ball is in contact with the wall …
5. ### physics

A 3.56-kg steel ball strikes a massive wall at 10.0 m/s at an angle of θ = 60.0° with the plane of the wall. It bounces off the wall with the same speed and angle (see the figure below). If the ball is in contact with the wall …
6. ### physics

A bullet is fired through a wall that is 10.0 cm. thick. The bullet entered the wall at 400. m/s, and it exited from the wall at 220. m/s. What was the average acceleration of the bullet while it was passing through the wall?
7. ### Physics URGENT!!!

A 4.02 kg steel ball strikes a massive wall at 11.8 m/s at an angle of 60.0° with the plane of the wall. It bounces off the wall with the same speed and angle, as shown in the figure below. If the ball is in contact with the wall …
8. ### physics

A 2.42 kg steel ball strikes a massive wall at 11.7 m/s at an angle of 60.0° with the plane of the wall. It bounces off the wall with the same speed and angle, as shown in the figure below. If the ball is in contact with the wall …
9. ### Physics

The brick wall (k=0.80 W/m°C) of a building has 4.0 m X 10.0m dimensions and 15cm thick. How much heat in joules flows through the wall in 12-hour period when the average inside and outside temperatures are 20°C and 50°C?
10. ### physics

A 3.42-kg steel ball strikes a massive wall at 10.0 m/s at an angle of θ = 60.0° with the plane of the wall. It bounces off the wall with the same speed and angle. If the ball is in contact with the wall for 0.170 s, what is …

More Similar Questions