Question

A 40 kg girl is pushing a 40 kg boy in a 20 kg toy wagon. The wagon is moving at a constant speed of 2.0 m/s. Calculate the combined kinetic energy of the boyWhat is the acceleration of a 50 kg object pushed with a force of 500 newtons?

Answer 1

Combined kinetic energy =120 joules

Acceleration=
`10 m/s^2`

Step-by-step explanation:

Given that the mass of the girl= 40 kg.

The mass of the boy= 40 kg.

The mass of the wagon = 20 kg.

The combined velocity of the boy and the wagon, v= 2.0 m/s.

The kinetic energy of any object having mass m and moving with the speed of v m/s, is

K.E.=
`\frac 1 2 mv^2`.

Here, the combined mass of the boy and the wagon = 40 + 20 = 60 kg.

So, the combined kinetic energy of the boy and the wagon

`=\frac 12 60 * 2^2= 120` J

When a force is applied on the object having the mass m, then

F=ma,

where a is the acceleration produced in the object.

Here, F=500 newtons and m= 50 kg.

so,
`500=50* a`

`\Rightarrow a = 500/50=10 m/s^2`.

Hence, the combined energy is 120 joules and the acceleration is 10
`m/s^2`.