Question
Coal is loaded into a train car while it is still moving If the mass of the train car doubles but the speed is decreased by half, what happened to the train's momentum? a It doubles b It gets cut in half It stays the same d it triples
Answer
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(242 Votes)
Molly
Master · Tutor for 5 years
Answer
Let's tackle this problem step by step, considering the concept of momentum in physics.【Tips】Momentum is a measure of the motion of an object and is calculated by the product of an object's mass and its velocity. The formula for momentum (p) is given by p = mv, where m is mass and v is velocity.【Description】Step 1: Consider the initial momentum of the train car before the coal is loaded. The initial momentum is given by the formula p = mv.Step 2: Let's denote the initial mass of the train car as 'm' and its initial speed as 'v'. So, the initial momentum is p_initial = m * v.Step 3: According to the problem, the mass of the train car doubles after loading the coal. Therefore, the new mass becomes 2m.Step 4: The problem also states that the speed of the train car is decreased by half. Therefore, the new speed becomes v/2.Step 5: Now, we calculate the new momentum of the train car after the coal is loaded. The new momentum is given by p_new = (2m) * (v/2).Step 6: Simplify the expression for the new momentum: p_new = 2m * v/2 = m * v.Step 7: By comparing the initial momentum (p_initial = m * v) with the new momentum (p_new = m * v), we can see that they are equal.Therefore, the momentum of the train car stays the same after the coal is loaded, even though its mass doubles and its speed is decreased by half.The accurate answer is:c. It stays the same