Question

A ball rolls up a slope. At the end of three seconds its velocity is 20 cm/s, at the end of eight seconds its velocity is 0. What is the average acceleration from the third to the eighth second?

• A. 2.5 cm/s²
• B. 4.0 cm/s²
• C. 5.0 cm/s²
• D. 6.0 cm/s²

Hint:

Remember that average acceleration is the change in velocity divided by the change in time, and it can be negative if the object is decelerating.

Answer 1

The Correct Option is B

The average acceleration is given by: \[ a = \frac{v_f - v_i}{t_f - t_i} \] where \( v_f = 0 \), \( v_i = 20 \, \text{cm/s} \), \( t_f = 8 \, \text{s} \), and \( t_i = 3 \, \text{s} \). Thus: \[ a = \frac{0 - 20}{8 - 3} = \frac{-20}{5} = -4 \, \text{cm/s}^2 \] So the average acceleration is \( 4.0 \, \text{cm/s}^2 \) in the opposite direction.