Question

A boy weighing blank kilograms is riding a skateboard. He’s moving at 2 meters/second and has 40 joules of kinetic energy. He doubles his speed when he sees his friends ahead of him. His kinetic energy at the faster speed is blank joules.

Answer 1

Answer:

80 kg, 160 j

Step-by-step explanation:

Answer 2

Answer:

His kinetic energy at the faster speed is 160 J

Step-by-step explanation:

Here in this question, we are interested in calculating the kinetic energy at the faster speed.

Firstly, we need to know the mass of the boy’s body. We can do this by using the kinetic energy formula;

Mathematically;

K.E = 1/2 * m * v^2

From the question;

K.E = 40 Joules

m = ?

v = speed = 2 m/s

Now, plugging these values into the kinetic energy equation, we have;

40 = 1/2 * m * 2^2

40 = 1/2 * m * 4

40 = 4m/2

4m = 40 * 2

4m = 80

m = 80/4

m = 20 kg

Now that we know the mass of the boy’s body, we can proceed to calculate the new K.E

Let’s follow the third statement in the question;

We were told that he doubles his speed upon sighting his friend.

Recall, he was traveling at a speed of 2 m/s.

Now doubling this means the new speed will

be 2 * 2 = 4 m/s

Now, we want to calculate the kinetic energy value at this new speed.

Mathematically, we use the same formula for kinetic energy.

K.E = 1/2 * m * v^2

We know that m is the mass that we calculated as 20kg and our v here is 4 m/s

Plugging these values, we have;

K.E = 1/2 * 20 * 4^2

K.E = (20 * 16)/2

K.E = 320/2

K.E = 160 J