Motion：练习题

Which feature of a distance-time graph represents the speed of an object?

An object is moving along a straight path. A speed-time graph of its motion shows a horizontal line at \(v = 12\text{ m/s}\) for \(5.0\text{ s}\), followed by a straight line with a negative gradient that reaches \(v = 0\) at \(t = 11\text{ s}\).

What is the total distance covered by the object during the entire \(11\text{ s}\) journey?

A train travels at a constant speed of \(20\text{ m/s}\). The driver applies the brakes, and the train decelerates uniformly to rest in \(40\text{ s}\).

How far does the train travel after the brakes are applied?

On a distance-time graph, which feature represents the speed of the object?

A distance-time graph for a moving car is a straight line that passes through the origin and has a constant positive gradient.

Which statement describes the acceleration of the car?

State the formula used to calculate average speed and identify the units used for each quantity in the formula according to the SI system.

A car is travelling at a constant velocity of \(15\text{ m/s}\). The driver observes an obstacle and applies the brakes, causing the car to decelerate uniformly at a rate of \(3.0\text{ m/s}^2\) until it reaches a speed of \(6.0\text{ m/s}\).

Calculate the time interval during which the brakes were applied.

A skydiver is falling at terminal velocity. Explain the relationship between the downward force of weight and the upward force of air resistance at this stage.

A train travels a distance of \(300\text{ m}\) along a straight track at a constant speed in \(15\text{ s}\).

What is the average speed of the train?

A train travels between two stations, A and B. It starts from rest at station A and accelerates uniformly at \(0.50\text{ m/s}^2\) for a time of \(40\text{ s}\). It then maintains this constant speed for \(2.0\text{ minutes}\) before decelerating uniformly to rest at station B in a further \(20\text{ s}\).

(a) Calculate the maximum speed reached by the train.
(b) Determine the total distance between station A and station B.
(c) Calculate the average speed for the entire journey.
(d) Describe the shape of the speed-time graph during the final \(20\text{ s}\) and state what the gradient of this line represents.