Question

Directions: Calculate the following problems using the formula below. Formula is KE = ½ of the mass × velocity squared 1. A car with a mass of 700 kg is moving with a speed of 20m/s. Calculate the kinetic energy of the car. 2. A cyclist and bike have a total mass of 100 kg and a speed of 15 m/s. Calculate the kinetic energy. 3. A tennis ball is traveling at 50 m/s and has a kinetic energy of 75 J. Calculate the mass of the tennis ball. 4. A 30 gram bullet travels at 300 m/S. How much kinetic energy does it have

Answer 1

1. 140000 J

2, 11250 J

3. 60g

4. 1350J

Step-by-step explanation:

1. The formula for kinetic energy is given so you just need to recognize the values. The unit for velocity is m/s or anything equivalent like km/h or mph. So here the only value matching the unit is 20 m/s. The unit of mass is kg or anything equivalent like g, ton etc so 700 kg is the mass. Now just plug in the values in the formula:

K.E=
`(1)/(2)`m(v)^2

=
`(1)/(2)`×700×(20)^2= 140000 J

2. Repeat the same process:

K.E=
`(1)/(2)`m(v)^2

=
`(1)/(2)`×100×(15)^2= 11250 J

3. The formula of K.E is J so plug in the values and use your algebra skills to make mass the subject (isolate it):

75=
`(1)/(2)` m×(50)^2

75= 2500m/2

75×2= 2500

m= 150/2500= 0.06 kg= 60g

4. Repeat just like 1 and 2:

Now look, the base unit of K.E is kg m^2/s^2 which means that if you want to get the answer in J you have to make all units the same as the base unit so 30/1000= 0.03

K.E=
`(1)/(2)` × 0.03 × (300)^2= 1350J