2.1.1 Reading Quiz - Mechanics

The correct answer is "rate of change of velocity". Acceleration is defined as the rate at which an object's velocity changes over time. It measures how quickly an object's speed or direction changes. Therefore, the rate of change of velocity is the most accurate explanation for acceleration.

Displacement is a vector quantity that refers to the distance and direction from a fixed point. It is different from distance, which only measures the length of the path traveled. Displacement takes into account both the magnitude and direction of the movement, providing a more comprehensive description of an object's change in position.

The gradient of a velocity-time graph represents the rate of change of velocity with respect to time. Since acceleration is defined as the rate of change of velocity, the gradient of a velocity-time graph gives the instantaneous acceleration.

The gradient of a displacement-time graph represents the rate of change of displacement with respect to time. This rate of change is equivalent to the velocity of an object at a specific moment in time. Therefore, the correct answer is instantaneous velocity.

Average velocity is defined as the displacement travelled divided by the time taken. Displacement refers to the change in position from the starting point to the ending point, while time refers to the duration of the journey. By dividing the displacement by the time, we obtain the average velocity, which represents the overall change in position per unit time. This measure is different from average speed, which only considers the total distance travelled divided by the time taken.

When a stone is thrown vertically upwards, it reaches its highest point when its velocity is zero. At this point, the stone momentarily stops moving upwards and starts to fall back downwards due to the force of gravity. However, the acceleration of the stone at its highest point is still 10ms-2, as gravity continues to act on it and accelerate it downwards. Therefore, the correct answer is "velocity is zero, acceleration is 10ms-2".

When a ball is thrown downward from the top of a tower, it experiences the force of gravity acting in the downward direction. This force causes the ball to accelerate in the same direction as gravity, which is downward. The magnitude of this acceleration is equal to the acceleration due to gravity, denoted as "g". Therefore, the correct answer is "exactly g". The downward acceleration of the ball will be equal to the acceleration due to gravity.

The stone will have fallen 500m after 10 seconds because the distance fallen by an object in free fall is determined by the equation d = 1/2gt^2, where d is the distance, g is the acceleration due to gravity (approximately 9.8 m/s^2), and t is the time. Plugging in the values, we get d = 1/2 * 9.8 * (10^2) = 1/2 * 9.8 * 100 = 490m. Rounded to the nearest meter, the stone will have fallen 500m after 10 seconds.

When an object is dropped from a plane flying at a constant speed in a straight line, it will continue to move horizontally with the same velocity as the plane. Since there is no air resistance, there are no external forces acting on the object horizontally. Therefore, the object will remain vertically under the plane as it falls vertically due to gravity.

The gradient of a distance-time graph represents the rate at which the distance is changing with respect to time. Instantaneous speed is the magnitude of the instantaneous velocity, which is the rate at which an object is moving at a particular moment in time. Therefore, the gradient of a distance-time graph gives the instantaneous speed.