Evaluate ut - $\frac{1}{2}$ft2 when t = 5, u = -20 and f = 10

Analyze the question: We need to evaluate the expression ut − ½ft² (the "t2" is t squared) by substituting u = -20, f = 10 and t = 5.

Concept: This looks like the motion formula s = ut − ½ft². Substitute carefully, and remember that t² is calculated before multiplying, and that a negative number times a positive number gives a negative result.

Solution:

1. Calculate ut: ut = (-20)(5) = -100

2. Calculate ½ft²: t² = 5² = 25 ½ × 10 × 25 = 5 × 25 = 125

3. Subtract: ut − ½ft² = -100 − 125 = -225

Answer: The value is -225, which matches option E.

Tip: In substitution questions, put negative values in brackets, such as (-20)(5), so you don't lose the sign. Also, square t first (t² = 25) before multiplying by the other numbers. Here both terms are negative (-100 and -125), so they add up in the negative direction.