Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. in one test, this gun accelerates a 5.0-kg projectile from rest to a speed of 4.0 × 103 m/s. the net force accelerating the projectile is 4.9 × 105 n. how much time is required for the projectile to come up to speed?

The time taken by the projectile to reach the required speed is 41 ms.

Calculate the acceleration  a of the projectile of mass m, using Newton's second law.

Substitute 5 kg for m and 4.9×10⁵N for F, the force needed for acceleration.

Use the equation of motion to determine the time taken by the projectile to reach a speed v from rest under the acceleration calculated.

Substitute 4.0×10³m/s for v, 0 for u and 9.8×10⁴m/s² for a.

The time taken to reach the required speed is 41 ms.

i think it is non rem sleep

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form