Question

A running back (m = 90 kg) is running (with the ball) at 3 m/s towards the East end zone. A linebacker (m = 130 kg) is running west at 3.5 m/s and tackles the running back. Define east as positive. 1.) Assuming the two football players become entangled, what is the direction and speed of both of them the moment after the hit? a.) about 3.3 m/s, East b.) about 0.85 m/s, East c.) about 0.85 m/s, West d.) about 3.3 m/s, West e.) about 1.42 m/s, East f.) about 1.42 m/s, West g.) about 2.1 m/s, East h.) about 2.1 m/s, West i.) None of these 2.) What direction would friction, acting upon the entangled football players, have to apply an impulse toward in order to stop them? a.) east b.) west c.) Since friction is an internal force to the system, no impulse is applied d.) None of these 3.) Suppose a lower friction surface (shorter grass, or snow on the field) was present during the tackle. Select the true statement. a.) Since conservation of momentum applies, the football players would take the same amount of time to stop sliding b.) Since friction is an internal force to the system of the football players, the players would take the same amount of time to stop sliding c.) Since conservation of momentum applies, the football players would take a longer time to stop sliding d.) Lower friction would mean a smaller outside force is applied, which would require a longer stopping time, according to the definition of impulse e.) none of these 4.) If the linebacker instead had a mass of 85 kg, how would this change the outcome of this problem? a.) Since his mass is now smaller than the running back's, the tackling would have happened in the opposite direction b.) Since conservation of momentum applies, his lower mass would have been balanced by a faster speed... leaving the outcome unchanged c.) The outcome (answer to number 16) depends on the combination of his velocity and mass compared to that of the running back's d.) If his mass were now smaller, the equation would not balance, and since the final momentum must remain unchanged, this would be an impossible situation. e.) none of these

          A running back (m = 90 kg) is running (with the ball) at 3 m/s towards the East end zone. A linebacker (m = 130 kg) is running west at 3.5 m/s and tackles the running back. Define east as positive.
1.) Assuming the two football players become entangled, what is the direction and speed of both of them the moment after the hit?
a.) about 3.3 m/s, East
b.) about 0.85 m/s, East
c.) about 0.85 m/s, West
d.) about 3.3 m/s, West
e.) about 1.42 m/s, East
f.) about 1.42 m/s, West
g.) about 2.1 m/s, East
h.) about 2.1 m/s, West
i.) None of these

2.) What direction would friction, acting upon the entangled football players, have to apply an impulse toward in order to stop them?
a.) east
b.) west
c.) Since friction is an internal force to the system, no impulse is applied
d.) None of these

3.) Suppose a lower friction surface (shorter grass, or snow on the field) was present during the tackle. Select the true statement.
a.) Since conservation of momentum applies, the football players would take the same amount of time to stop sliding
b.) Since friction is an internal force to the system of the football players, the players would take the same amount of time to stop sliding
c.) Since conservation of momentum applies, the football players would take a longer time to stop sliding
d.) Lower friction would mean a smaller outside force is applied, which would require a longer stopping time, according to the definition of impulse
e.) none of these

4.) If the linebacker instead had a mass of 85 kg, how would this change the outcome of this problem?
a.) Since his mass is now smaller than the running back's, the tackling would have happened in the opposite direction
b.) Since conservation of momentum applies, his lower mass would have been balanced by a faster speed... leaving the outcome unchanged
c.) The outcome (answer to number 16) depends on the combination of his velocity and mass compared to that of the running back's
d.) If his mass were now smaller, the equation would not balance, and since the final momentum must remain unchanged, this would be an impossible situation.
e.) none of these

Added by Anita P.

Question

Please give Ace some feedback