Fred (mass 61 kg ) is running with the football at a speed of 5.9 m/swhen he is
ID: 1428285 • Letter: F
Question
Fred (mass 61 kg ) is running with the football at a speed of 5.9 m/swhen he is met head-on by Brutus (mass 120 kg ), who is moving at 4.0 m/s . Brutus grabs Fred in a tight grip, and they fall to the ground.
How far do they slide? The coefficient of kinetic friction between football uniforms and Astroturf is 0.30.
Express your answer to two significant figures and include the appropriate units in CM
Fred (mass 61 kg ) is running with the football at a speed of 5.9 m/swhen he is met head-on by Brutus (mass 120 kg ), who is moving at 4.0 m/s . Brutus grabs Fred in a tight grip, and they fall to the ground.
How far do they slide? The coefficient of kinetic friction between football uniforms and Astroturf is 0.30.
Express your answer to two significant figures and include the appropriate units in CM
Explanation / Answer
First let's find their initial combined velocity after collision by using conservation of momentum
Fred's momentum is 61kg*(5.9m/s)=359.9 let's say to the right
Brutus' momentum is 120 kg*(4.0m/s)=480 to the left so we'll make this negative.
add these together and figure the final velocity based on combined mass
359.9 - 480 =(61+120)v2
v2=-120.1/181
v2 = -0.66 or 0.66 m/s to the left
The frictional force will be the friction coefficient times their combined weight
Ff= 0.3(181)(9.81) = 532.7 N
Balancing work equations
1/2mv^2-FfD=0
D=1/2mv^2/Ff
D= 1/2 (181)(0.66^2)/532.7
D=0.074 m
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