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Math

Math Snap

PROBLEM

1 ■
Mark for Review
A hawk with mass 1 kg dives straight downward. At time t1t_{1}, the hawk has a speed of 20 m/s20 \mathrm{~m} / \mathrm{s}. At time t2t_{2}, the hawk has a speed of 50 m/s50 \mathrm{~m} / \mathrm{s}. The change in the kinetic energy of the hawk between t1t_{1} and t2t_{2} is most nearly
(A) 200 J
(B) 450 J
(C) 1050 J
(D) 1250 J

STEP 1

1. The mass of the hawk is 1 kg.
2. The initial speed of the hawk at time t1 t_1 is 20m/s 20 \, \mathrm{m/s} .
3. The final speed of the hawk at time t2 t_2 is 50m/s 50 \, \mathrm{m/s} .
4. We are asked to find the change in kinetic energy of the hawk between t1 t_1 and t2 t_2 .

STEP 2

1. Recall the formula for kinetic energy.
2. Calculate the initial kinetic energy at t1 t_1 .
3. Calculate the final kinetic energy at t2 t_2 .
4. Determine the change in kinetic energy.

STEP 3

Recall the formula for kinetic energy, which is given by:
KE=12mv2 KE = \frac{1}{2} m v^2 where m m is the mass and v v is the velocity.

STEP 4

Calculate the initial kinetic energy at t1 t_1 using the formula:
KE1=12×1kg×(20m/s)2 KE_1 = \frac{1}{2} \times 1 \, \mathrm{kg} \times (20 \, \mathrm{m/s})^2 KE1=12×1×400 KE_1 = \frac{1}{2} \times 1 \times 400 KE1=200J KE_1 = 200 \, \mathrm{J}

STEP 5

Calculate the final kinetic energy at t2 t_2 using the formula:
KE2=12×1kg×(50m/s)2 KE_2 = \frac{1}{2} \times 1 \, \mathrm{kg} \times (50 \, \mathrm{m/s})^2 KE2=12×1×2500 KE_2 = \frac{1}{2} \times 1 \times 2500 KE2=1250J KE_2 = 1250 \, \mathrm{J}

SOLUTION

Determine the change in kinetic energy by subtracting the initial kinetic energy from the final kinetic energy:
ΔKE=KE2KE1 \Delta KE = KE_2 - KE_1 ΔKE=1250J200J \Delta KE = 1250 \, \mathrm{J} - 200 \, \mathrm{J} ΔKE=1050J \Delta KE = 1050 \, \mathrm{J} The change in kinetic energy of the hawk between t1 t_1 and t2 t_2 is most nearly:
1050J \boxed{1050 \, \mathrm{J}}

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