1) A ball with a mass of 1.5kg falls on a floor vertically at 25m/s and bounces

Question

1) A ball with a mass of 1.5kg falls on a floor vertically at 25m/s and bounces back vertically at 15m/s. The magnitude of the impulse of the flood (in kg-m/s) on the ball is:

2)A ball 250g is droppd from the top of a building just before it hits the ground, its kinetic energy is 58J. How high is the building?

3)A projectile is thrown at 10m/s making an angle of 60 degrees above the horizontal. How high from its original position will the projectile be when it is at its highest point during the flight? Use the energy concepts in solving this problem?

Explanation / Answer

(1)

Impulse F*t = m*v = 1.5* (25-(-15)) = 60 Ns

(2)

K.E. = 1/2*m*v^2 = 58 J

v^2 = 2*58/0.25

v = 21.54 m/s

height of the bulding

h = v^2/2*g = 464/2*9.81 =23.65 m/s

(3)

Vertical speed, vy = 10*sin 60 = 8.66 m/s

K.E. @ bottom = PE @ heighest point

1/m*vy^2 = m*g*h

Heighest point during the flight,

h = vy^2/2*g = 75/2*9.81 = 3.82 m

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