A power boat, starting from rest, maintains a constant acceleration. After a cer

Question

A power boat, starting from rest, maintains a constant acceleration. After a certain time Delta t, its displacement and velocity are Delta r and Delta v. After a time of 2 Delta t, what would be its displacement and velocity? a. 2 Delta r and 2 Delta v b. Delta r and 4 Delta v c. 4 Delta 2 Delta v d. 4 Delta r and 4 Delta v A convertible with its top down is moving at a constant velocity along a long straight road. If a rifle is pointing straight up from the car and is then fired what best describes were the bullet will land (Ignore air resistance). a. behind the car b. ahead of the car c. in the rifle barrel d. Need to know At what angle would a projectile need to be fired to achieve the greatest range. a. 45 degree b. 0 degree c. 65 degree d. 90 degree

Explanation / Answer

(1) kinematic equation for constant acceleration,starting from rest are

x = (1/2)*a*t^2

v = a*t

when t = T

r = (1/2)*a*T^2

V = a*T

when t = 2T

r' = (1/2)*a*(2T)^2

= 4*[(1/2)*a*T^2]

= 4*r

V' = a*(2T)

= 2(a*T)

= 2V

4r and 2v (c)

(2) the bullet remains directly above the rifle at all times and would fall directly back into the barrel of the rifle.

(c) in the rifle barrel

(3) the greatest range is 45 degree.

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