Question

1. Mary has a mass of 40 kg and sprints at 1 m/s. How much kinetic energy does she have?

Answer 1

Answer:

1. Mary has 20 joules of Kinetic energy

2. Yes his kinetic energy be twice as much

3. If Roberto runs twice as fast, his Kinetic energy will be 4 times as much

4. 16875 Joules

5. 5.77 m/s

6. 8 kg

7. 345600 J

Explanation:

The formula for Kinetic Energy is given as $KE= 0.5\times m \times v^{2}$

We will apply this in solving all the problems below using the parameters provided by each problem.

1. Mary's Kinetic Energy will be equal to $0.5 \times 40 \times 1^{2}=20joules$

2a. If Roberto has twice Mary's mass, his mass will be 80 kg.

His K.E will be $KE= 0.5\times 80 \times 1^{2}= 40 joules$

2b. If Roberto runs twice as fast, his kinetic energy will be $KE= 0.5\times 80 \times 2^{2}= 160 joules$. This is four times its initial value

4. $KE= 0.5\times 150 \times 15^{2}= 16875 joules$

5. $v=\sqrt{\frac{500}{0.5 \times 30}}=5.77m/s$

6. $mass, m = \frac{100}{0.5 \times 5^{2}}= 8kg$

7. $KE= 0.5\times 1200 \times 24^{2}= 345600 joules$