![](../../image/prcpywrt.gif)
Suppose that a cannon is used to launch a projectile into Earth orbit as Newton proposed. Assume that the cannon
accelerates its shell at 20 times the acceleration due to gravity and achieves orbital velocity of 8000m/s. How long must the
cannon be?
(A) 8000m.
(B) 80,000m.
(C) 160,000m.
(D) 10m.
![](../../image/prcpywrt.gif)
Suppose that a cannon is used to launch a projectile into Earth orbit as Newton proposed. Assume that the cannon
accelerates its shell at 20 times the acceleration due to gravity and achieves orbital velocity of 8000m/s. How long must the
cannon be?
(A) 8000m. --- No.
The acceleration is 200m/s
.
![](../../image/prcpywrt.gif)
Suppose that a cannon is used to launch a projectile into Earth orbit as Newton proposed. Assume that the cannon
accelerates its shell at 20 times the acceleration due to gravity and achieves orbital velocity of 8000m/s. How long must the
cannon be?
(B) 80,000m. --- No.
Remember the factor of 2 in the formula:
v
=2ad.
![](../../image/prcpywrt.gif)
Suppose that a cannon is used to launch a projectile into Earth orbit as Newton proposed. Assume that the cannon
accelerates its shell at 20 times the acceleration due to gravity and achieves orbital velocity of 8000m/s. How long must the
cannon be?
(C) 160,000m. --- Yes.
d = v
/(2a) = (8000m/s)
/(400m/s
)
= (64,000,000)/(400) m = 160,000m.
![](../../image/prcpywrt.gif)
Suppose that a cannon is used to launch a projectile into Earth orbit as Newton proposed. Assume that the cannon
accelerates its shell at 20 times the acceleration due to gravity and achieves orbital velocity of 8000m/s. How long must the
cannon be?
(D) 10m. --- No.
Remember to multiply the velocity by itself to get the velocity squared.