Final answer:
To calculate acceleration, the variables that must be known are time and velocity. Acceleration is the rate of change of velocity over time. Other concepts such as force and mass relate to Newton's second law and are not directly required for calculating acceleration.
Step-by-step explanation:
To calculate acceleration, you must know the variables of time and velocity (or speed if direction is constant). Acceleration is defined as the rate at which velocity changes with respect to time. Therefore, the correct answer from the options provided is A) Time and speed. This is because acceleration can be calculated using the formula acceleration = change in velocity / change in time. It's important to note that velocity includes both speed and direction, making it a vector quantity, whereas speed is a scalar quantity.
Regarding Newton's second law, it describes the relationship between force, mass, and acceleration, and it can be expressed as force = mass × acceleration. However, this doesn't directly answer the question of which variables are needed to calculate acceleration alone.
If we consider the options given in a check your understanding format:
- Acceleration, Displacement, Time, and Velocity (b) are the four variables found in the kinematic equations.
- Displacement, velocity, acceleration (b) contains two vectors and a scalar.
- The rate at which velocity changes (c) correctly defines acceleration.