Question

Point out the mistakes in the following cases.
(a) Two cars move for 5 minutes and 2 minutes respectively. The second car is faster because it takes less time.
(b) Two cars move at a speed of 45 km/h. Their velocities are the same.
(c) Trains moving in the same direction have the same velocity.
(d) A motorist travels 600 km. Another motorist travels only 560 km. the second car is slower than the first.

Answer 1

(a) The distances travelled by the two cars are not given; these are required to calculate the speeds of the cars and to evaluate which car is faster. Hence, we cannot say that the second car is faster than the first car.

(b) If both the cars are moving at a speed of 45 km/h, then it is not necessary that their velocities are also the same because the directions of motion are not given.

(c) For the same velocity, the magnitudes and directions must be the same, but only direction is given in the statement.

(d) Time, which is required to calculate the speeds of the cars and to evaluate which motorist is slower, is not given. Hence, we cannot say that the second car is slower than the first.