Question

If an object of mass 5kg changes its velocity from 10m/s to 40m/s under the
application of a force then calculate the work done by force applied?

Answer 1

3750 J is the required answer.

GIVEN:

• Mass, m = 5 kg

• Initial velocity, u = 10 m/s

• Final velocity, v = 40 m/s

TO FIND:

Work done, w

FORMULA:

• According to first equation of motion , v = u + at

• According to third equation of motion, V²- u² = 2as

• According to Newton's second law of motion, f = ma

• Work done , w = f s

Where

• a is the acceleration
• s is the distance moved
• t is the time

SOLUTION:

STEP 1: TO FIND ACCELERATION:

v = u + at

40 = 10 + at

30 = at

a = 30/t m/s²

STEP 2 : TO FIND FORCE:

f = ma

f = 5 × (30 / t)

f = 150/t N

STEP 3 : TO FIND DISTANCE S:

V²- u² = 2as

40² - 10² = 2 × (30/t) × s

1600 - 100 = (60/t) × s

1500 = (60 /t) × s

1500 × ( t/ 60) = s

(150 t ) / 6 = s

(50 t) / 2 = s

s = 25t metre

STEP 4 : TO FIND WORK DONE:

w = fs

w = (150 / t) × (25 t)

w = 150 × 25

w = 3750 joules

ANSWER:

Work done by applied force is 3750 joules.