In the previous section, you briefly learned about the law of acceleration. As noted in the video, this information is calculated using the formula Fnet = ma. Before practicing these calculations, let’s take a moment to look at each part of the equation. Move your cursor over each variable to find out what it represents.

Often, you have a portion of the information for a problem, but it may not be exactly what you need to solve the equation easily. For example, you may have force and mass, but not acceleration. When working on these problems, it is helpful to complete the following steps:

  1. List the variables.
  2. Next to the variable, list the information you do have.
  3. Use your algebra skills to work through the equation. For example, if you have mass and force, you may need to adjust the equation for finding acceleration as follows: F net over Mass Fnet mass = acceleration to find acceleration.

Let’s practice calculating the law of acceleration in the problems below.

Practice

For the following questions, calculate the value of the unknown variable.

  1. The net external force on the propeller of a 3.2 kg model airplane is 7.0 N forward. What is the acceleration of the airplane?

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    Check Your Answer

    Using F = ma, we can find the unknown "a" by dividing through m to produce a = F/m = 7.0 N/3.2 kg = 2.2 m/s2 forward.Close Pop Up

  2. The net external force on a golf cart is 390 N North. If the cart has a total mass of 270 kg, what are the magnitude and direction of its acceleration?

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    Check Your Answer

    Using F = ma, we can find the unknown "a" by dividing through m to produce a = F/m = 390 N/270 kg = 1.4 m/s2 north.Close Pop Up

  3. A car has a mass of 1500 kg. If the force acting on the car is 6750 N to the east, what is the car’s acceleration?

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    Check Your Answer

    Using F = ma, we can find the unknown "a" by dividing through m to produce a = F/m = 6750 N/1500 kg = 4.5 m/s2 east.Close Pop Up

  4. A soccer ball kicked with a force of 13.5 N accelerates at 6.5 m/s2 to the right. What is the mass of the ball?

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    Check Your Answer

    Using F = ma, we can find the unknown "m" by dividing through a to produce m = F/a = 13.5 N/6.5 m/s2 = 2.1 kg.Close Pop Up