If a 1000-kg car was moving at 30 m/s, what would be its kinetic energy expressed in the unusual (for kinetic energy) units of calories? (1 cal = 4.186 J)

a. 3.0 * 104

b. 9.0 * 105

c. 3.8 * 106

d. 1.1 * 105

(d). 1.1 * 10⁵ cal.

Explanation:

Kinetic Energy of a body: This is the energy of a body i motion. It is measured in Joules.

It can be expressed mathematically as

Ke = 1/2mv² ... equation 1

Where ke = kinetic energy, m = mass in kg, v = velocity in m/s.

Where m = 1000 kg, v = 30m/s.

Substiting these values into equation 1,

Ke = 1/2 (1000) (30) ²

Ke = 500 * 900 = 450000 J

If 1 cal = 4.186 J

4.186 J = 1 cal

450000 J = (450000 * 1) / 4.186 cal

= 107501.2 cal. = 1.075 * 10⁵ cal

The Kinetic Energy is ≈ 1.1 * 10⁵ cal.

The right option is (d) 1.1 * 10⁵ cal.