Question

What is the amount of energy used in making a body of mass 20 kg to move through a distance of 40m by applying a force that makes the body move from rest to a speed of 10m/s in 5 seconds?(only answer) *​

Answer 1

Given :-

• mass, m = 20 kg
• displacement, s = 40 m
• initial velocity, u = 0 m/s
• final velocity, v = 10 m/s
• time, t = 5 s

To Find :-

• amount of energy used ?

Solution :-

we know by Newton's first law of motion,

$\boxed{\bold{at = {v - u}}}$

$\bold{: \implies 5a = 10 - 0 } \\ \\ \bold{: \implies a = \cancel \frac{10}{5} } \: \: \: \: \: \: \: \: \: \\ \\ \bold{: \implies a = 2 \: m {s}^{ - 2} } \:$

so, acceleration is 2 m/s²

and we know that,

$\boxed{ \bold{force = mass \times acceleration}}$

$\bold{: \implies f = 20 \times 2} \\ \\ \bold{: \implies f = 40 \:N } \: \:$

so, force exerted is 40 N

and now,

$\boxed{\bold{work = force \times displacement}}$

$\bold{: \implies w = 40 \times40 } \\ \\ \bold{: \implies w = 1600 } \: \: \: \: \:$

so, work done is 1600 Joules

and this work is energy

hence, energy used is 1600 Joules