11 Skaters of masses 80 kg and 40 kg move directly towards each other and collide.Before the collision, the heavier skater is moving to the right at a speed of 2.0 m s –1 and the lighterskater is moving to the left at a speed of 1.0 m s –1.After the collision, the heavier skater moves to the right at a speed of 0.80 m s –1.What is the relative speed of separation of the two skaters?A 0.6 m s –1 B 1.4 m s –1 C 2.2 m s –1 D 2.6 m s –112 Which statement describes the two forces in a couple?A They act in the same direction.B They act through the same point.C They produce zero resultant force.D They produce zero resultant moment
Question
11 Skaters of masses 80 kg and 40 kg move directly towards each other and collide.Before the collision, the heavier skater is moving to the right at a speed of 2.0 m s –1 and the lighterskater is moving to the left at a speed of 1.0 m s –1.After the collision, the heavier skater moves to the right at a speed of 0.80 m s –1.What is the relative speed of separation of the two skaters?A 0.6 m s –1 B 1.4 m s –1 C 2.2 m s –1 D 2.6 m s –112 Which statement describes the two forces in a couple?A They act in the same direction.B They act through the same point.C They produce zero resultant force.D They produce zero resultant moment
Solution
The question seems to be cut off, but I'll answer the parts that are complete.
For the first question, we need to find the speed of the lighter skater after the collision. We can use the principle of conservation of momentum for this. The total momentum before the collision is equal to the total momentum after the collision.
Before the collision, the total momentum is (80 kg * 2.0 m/s) + (40 kg * -1.0 m/s) = 120 kg*m/s.
After the collision, the total momentum is (80 kg * 0.80 m/s) + (40 kg * v), where v is the velocity of the lighter skater.
Setting these equal to each other gives us 120 kgm/s = 64 kgm/s + 40 kg * v. Solving for v gives us v = 1.4 m/s.
The relative speed of separation of the two skaters is the difference in their speeds, which is 1.4 m/s - 0.80 m/s = 0.6 m/s. So the answer is A, 0.6 m/s.
For the second question, a couple consists of two parallel forces that are equal in magnitude, opposite in direction and not along the same line. This means they produce a moment or turning effect but no resultant force. So the answer is D, they produce zero resultant moment.
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