Question

If a body of mass 5kg is moving along a straight line with velocity 10m/s and acceleration 20m/s².Find its kinetic energy after 10s.

Answer 1

Given :

Mass of the body = 5 kg

Initial velocity = 10 m/s

Acceleration = 20 m/s²

To Find :

Kinetic energy of the body after 10 s.

Solution :

Before finding kinetic energy we have to calculate final velocity of the body at the end of 10 s.

• Acceleration is defined as the rate of change of velocity per unit time.

Mathematically;

$:\implies\:\underline{\boxed{\bf{\red{a=\dfrac{v-u}{t}}}}}$

• a denotes acceleration

• v denotes final velocity

• u denotes initial velocity

• t denotes time

By substituting the given values;

→ 20 = (v - 10) / 10

→ v - 10 = 20 × 10

→ v = 200 + 10

→ v = 210 m/s

★ Kinetic energy of the body :

→ k = 1/2 × m × v²

→ k = 1/2 × 5 × (210)²

→ k = 1/2 × 220500

→ k = 110250 J = 110.2 kJ