Force
An object has a mass of 2 kg and accelerates at 5 m/s². What is the force?
F = ma = 2 × 5 = 10 N
A person pushes a box with a force of 10 N for 2 meters. How much work is done?
W = F × d = 10 × 2 = 20 J
A student does 100 J of work in 10 seconds. What is the power output?
P = W ÷ t = 100 ÷ 10 = 10 W
What is the gravitational potential energy of a 2 kg object lifted 5 meters high?
(g = 9.8 m/s²)
GPE = mgh = 2 × 9.8 × 5 = 98 J
A sound wave travels 340 meters in 1 second. What is its speed?
v = d ÷ t = 340 ÷ 1 = 340 m/s
A 3 kg ball is kicked and accelerates at 4 m/s². What is the net force acting on the ball?
F = ma = 3 × 4 = 12 N
A crate is dragged 5 meters with a constant force of 25 N. How much work is done?
W = F × d = 25 × 5 = 125 J
A machine does 300 J of work in 20 seconds. How much power does it use?
P = 300 ÷ 20 = 15 W
Find the kinetic energy of a 3 kg object moving at 4 m/s.
KE = ½ × 3 × 4² = ½ × 3 × 16 = 24 J
If the frequency of a sound wave is 170 Hz and the wavelength is 2 m, what is the wave speed?
v = λ × f = 2 × 170 = 340 m/s
A force of 60 N is applied to a box, causing it to accelerate at 3 m/s². What is the mass of the box?
m = F ÷ a = 60 ÷ 3 = 20 kg
How much force is needed to do 180 J of work over a distance of 6 meters?
F = W ÷ d = 180 ÷ 6 = 30 N
How much work is done if a motor produces 50 W of power for 4 seconds?
W = P × t = 50 × 4 = 200 J
A backpack has 4.5 kg of mass and is placed on a shelf 2 meters high. What is its GPE?
GPE = 4.5 × 9.8 × 2 = 88.2 J
A sound wave takes 2 seconds to travel 600 meters. What is its speed?
v = d ÷ t = 600 ÷ 2 = 300 m/s
A 10 kg object is moving with an acceleration of 6 m/s². Then, a frictional force of 20 N opposes the motion. What total force must be applied to maintain this acceleration?
F_required = ma + friction = (10 × 6) + 20 = 60 + 20 = 80 N
A mover does 500 J of work to push a cart over a distance of 20 meters. What was the applied force?
F = W ÷ d = 500 ÷ 20 = 25 N
A person uses 180 watts of power to do a task in 6 seconds. How much work did they do?
W = P × t = 180 × 6 = 1,080 J
A spring with a constant of 200 N/m is compressed by 0.1 m. What is the elastic potential energy stored?
EPE = ½ × 200 × (0.1)² = 0.5 × 200 × 0.01 = 1 J
A medium has an elasticity constant of 1.6 × 10⁵ N/m² and a density of 1.0 kg/m³. What is the speed of sound in the medium?
v = √(1.6 × 10⁵ ÷ 1) = √160,000 ≈ 400 m/s
Two people push a 5 kg cart in the same direction. One applies 15 N, the other 10 N. A frictional force of 5 N opposes the motion. What is the cart’s acceleration?
Net force = 15 + 10 - 5 = 20 N → a = F ÷ m = 20 ÷ 5 = 4 m/s²
A worker applies a force of 40 N and does 320 J of work. How far did the object move?
d = W ÷ F = 320 ÷ 40 = 8 meters
A generator does 2,400 J of work in 3 minutes. What is its power output?
Convert time: 3 min = 180 sec
P = W ÷ t = 2400 ÷ 180 = 13.33 W
What is the velocity of a 10 kg object if it has 400 J of kinetic energy?
KE = ½ mv² → 400 = 0.5 × 10 × v² → 400 = 5v² → v² = 80 → v = √80 ≈ 8.94 m/s
If the bulk modulus of a substance is 2.25 × 10⁵ N/m² and its density is 1.5 kg/m³, what is the speed of sound?
v = √(2.25 × 10⁵ ÷ 1.5) = √150,000 ≈ 387.3 m/s