Practice Net Force in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

The single resultant force obtained by vector addition of all individual forces acting on an object, which alone determines the object's acceleration according to Newton's second law, F⃗net=ma⃗\vec{F}_{net} = m\vec{a}.

What you get when you add up all pushes and pulls, accounting for direction.

Showing a random 20 of 50 problems.

Example 1

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A 55 kg object feels 2020 N east and 1515 N west. Find its acceleration.

Example 2

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Two ropes tied to a heavy load pull at 40°40° on either side of vertical, each with tension T=100 NT = 100 \text{ N}. What is the magnitude of the net force from the ropes?

Example 3

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Three coplanar forces act on a particle: F1=6 NF_1 = 6 \text{ N} east, F2=4 NF_2 = 4 \text{ N} north, F3=6 NF_3 = 6 \text{ N} west. What is the magnitude of the net force?

Example 4

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An elevator of mass 500 kg500 \text{ kg} accelerates upward at 2 m/s22 \text{ m/s}^2. What is the net force, and what is the tension in the cable? Use g=9.8 m/s2g = 9.8 \text{ m/s}^2.

Example 5

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Forces of 33 N right, 55 N right, and 44 N left act on a block. Net force?

Example 6

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A 2 kg2 \text{ kg} block on a 25°25° frictionless incline is held by a rope pulled parallel to the slope with tension TT so the block stays at rest. What is TT? Use g=9.8 m/s2g = 9.8 \text{ m/s}^2.

Example 7

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A 10 kg10 \text{ kg} sled accelerates east at 1.5 m/s21.5 \text{ m/s}^2. What is the net force on the sled?

Example 8

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Three forces give a net force of zero. Two are 88 N north and 66 N east. What is the third force?

Example 9

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Two forces F⃗1=(3i^+4j^) N\vec F_1 = (3 \hat{i} + 4 \hat{j}) \text{ N} and F⃗2=(−1i^+2j^) N\vec F_2 = (-1 \hat{i} + 2 \hat{j}) \text{ N} act on a 1 kg1 \text{ kg} particle. Find the net force and resulting acceleration.

Example 10

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A 22 kg cart accelerates at 55 m/s2^2. What net force acts on it?

Example 11

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A car moves at a constant 2020 m/s in a straight line. What is the net force on it?

Example 12

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A 22 kg block on a 30∘30^\circ frictionless incline. Find its acceleration down the slope (g=10g=10 m/s2^2).

Example 13

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A 0.2 kg0.2 \text{ kg} ball is whirled on a 1 m1 \text{ m} vertical string. At the top of the loop, its speed is 4 m/s4 \text{ m/s}. What is the tension in the string? Use g=9.8 m/s2g = 9.8 \text{ m/s}^2.

Example 14

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A 0.50.5 kg ball changes velocity from 00 to 66 m/s in 22 s. What net force acted?

Example 15

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A box on a frictionless floor is pushed with 1515 N right and nothing opposes it horizontally. Net horizontal force?

Example 16

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A 50 kg50 \text{ kg} person stands in an elevator accelerating downward at 2 m/s22 \text{ m/s}^2. What is the net force on her, and what is the normal force from the floor? Use g=9.8 m/s2g = 9.8 \text{ m/s}^2.

Example 17

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A car of mass 1200 kg1200 \text{ kg} decelerates from 30 m/s30 \text{ m/s} to 00 over 6 s6 \text{ s}. What is the magnitude of the average net force on the car?

Example 18

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A 5 kg5 \text{ kg} block on a frictionless surface is pulled by a rope at 30°30° above horizontal with tension 20 N20 \text{ N}. What is the horizontal component of the net force?

Example 19

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A 0.5 kg0.5 \text{ kg} ball moves in a horizontal circle of radius 0.4 m0.4 \text{ m} at speed 2 m/s2 \text{ m/s}. What is the net force on the ball, and which direction?

Example 20

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Forces on an object: 10 N10 \text{ N} at 0°0°, 10 N10 \text{ N} at 120°120°, 10 N10 \text{ N} at 240°240°. Find the net force.
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