The horizontal and vertical components of the initial velocity of a football are

Question

The horizontal and vertical components of the initial velocity of a football are 20 m/s and 30 m/s respectively. Assume that after rising to some height, the football returns back to the ground level.

1. what is the speed of the football at t = 3 s after launch?

a) 10 m/s

b) 15 m/s

c) 20 m/s

d) 30 m/s

e) 50 m/s

2. to what maximum height does the football rise?

a) 10 m

b) 15 m

c) 30 m

d) 45 m

e) 60 m

3. what horizontal distance does the football travel during its flight?

a) 120 m

b) 100 m

c) 60 m

d) 40 m

e) 30 m

4. a projectile is shot at an angle of 60 degrees to the horizontal near the surface of the earth but in the absence of air resistance. when it reaches the highest point of its trajectroy, its speed is 150 m/s. the initial launch speed of the projectile is

a) 150 m/s

b)200 m/s

c) 250 m/s

d) 300 m/s

e) 400 m/s

5. A 50- kg man stands on a bathroom scale in an elevator. what does the scale read if the elevator is going downward with an ecceleration of 2.0 m/s^2?

a) 300 N
b) 400 N
c) 500 N
d) 600 N
e) 750 N

( please show calculations)

Explanation / Answer

1) Vy = uy - gt = 30-10*3 = 0m/s

V = sqrt(Vx^2+Vy^2)

c) 20 m/s

2) H = uy^2/2g = 900/20

d) 45 m


3) R = 2*Vx*Vy/g = (2*20*30)/10

a) 120 m


4) V*cos60 = 150

V = 150/cos60 = 300 m/s

5) W' = m*(g-a) = 50*(10-2) = 400N

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