1. A small ball is thrown horizontally with a constant speed of 10 m/s. The ball hits the wall and reflected with the same speed. What is the change in linear momentum of the ball?
Known :
Mass (m) = 0.2 kg
Initial speed (vo) = -10 m/s
Final speed (vt) = 10 m/s
The plus and minus sign indicates that the objects moves in opposite direction.
Wanted : the change in linear momentum (Δp)
Solution :
Formula of the change in linear momentum :
Δp = m vt – m vo = m (vt – vo)
The change in linear momentum :
Δp = 0.2 (10 – (-10)) = 0.2 (10 + 10)
Δp = 0.2 (20)
Δp = 4 kg m/s
2. A 10-gram ball falls freely from a height, hits the floor at 15 m/s, then reflected upward at 10 m/s. Determine the impulse!
Known :
Mass (m) = 10 gram = 0.01 kg
Initial velocity (vo) = -15 m/s
Final velocity (vt) = 10 m/s
Wanted : Impulse (I)
Solution :
The impulse (I) equals the change in momentum (Δp)
I = m vt – m vo = m (vt – vo)
Impulse :
I = 0.01 (10 – (-15)) = 0.01 (10 + 15)
I = 0.01 (25)
I = 0.25 kg m/s
3. A 200-gram ball thrown horizontally with a speed of 4 m/s, then the ball was hit in the same direction. The duration of the ball in contact with the bat is 2 milliseconds and the ball speed after leaving the bat is 12 m/s. The magnitude of force exerted by the batter on the ball is …
Known :
Mass (m) = 200 gram = 0.2 kg
Initial velocity (vo) = 4 m/s
Final velocity (vt) = 12 m/s
Time interval (t) = 2 milliseconds = (2/1000) seconds = 0.002 seconds
Wanted : The magnitude of the force (F)
Solution :
Formula of impulse :
I = F t
Formula of the change in momentum :
m vt – m vo = m (vt – vo)
The impulse (I) equals the change in momentum (Δp)
I = Δp
F t = m (vt – vo)
F (0.002) = (0.2)(12 – 4)
F (0.002) = (0.2)(8)
F (0.002) = 1.6
F = 1.6 / 0.002
F = 800 Newton
[wpdm_package id=’1155′]
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