Study Answers – Basic Physics Equations #
Speed (v = d/t) #
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Q: A cyclist travels 150 meters in 30 seconds. Calculate their speed.
v = d/t = 150/30 = 5 m/s
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Q: How long will it take a car traveling at 20 m/s to cover a distance of 400 meters?
t = d/v = 400/20 = 20 seconds
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Q: If a runner maintains a speed of 3 m/s for 45 seconds, what distance will they cover?
d = v × t = 3 × 45 = 135 meters
Acceleration (a = (v-u)/t) #
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Q: A car accelerates from rest to 15 m/s in 5 seconds. Calculate the acceleration.
a = (15 – 0)/5 = 3 m/s²
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Q: A train’s speed decreases from 30 m/s to 10 m/s in 4 seconds. What is its deceleration?
a = (10 – 30)/4 = -5 m/s² (negative indicates deceleration)
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Q: What time will it take for a bicycle to accelerate from 2 m/s to 8 m/s with an acceleration of 0.5 m/s²?
t = (v – u)/a = (8 – 2)/0.5 = 12 seconds
Momentum (p = mv) #
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Q: Calculate the momentum of a 5 kg bowling ball moving at 4 m/s.
p = mv = 5 × 4 = 20 kg⋅m/s
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Q: A 0.5 kg football has a momentum of 3 kg⋅m/s. What is its velocity?
v = p/m = 3/0.5 = 6 m/s
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Q: A car of mass 1200 kg is moving with a velocity of 20 m/s. Calculate its momentum.
p = mv = 1200 × 20 = 24000 kg⋅m/s
Weight (W = mg) #
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Q: Calculate the weight of a 75 kg person on Earth (g = 9.81 N/kg).
W = mg = 75 × 9.81 = 735.75 N
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Q: A box weighs 200 N on Earth. What is its mass?
m = W/g = 200/9.81 = 20.39 kg
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Q: Calculate the weight of a 2.5 kg book on Earth.
W = mg = 2.5 × 9.81 = 24.525 N
Density (ρ = m/V) #
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Q: A cube of metal has mass 800 g and volume 100 cm³. Calculate its density.
ρ = m/V = 800/100 = 8 g/cm³
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Q: The density of water is 1000 kg/m³. What is the mass of 2 m³ of water?
m = ρV = 1000 × 2 = 2000 kg
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Q: A material has density 2400 kg/m³ and mass 12 kg. Calculate its volume.
V = m/ρ = 12/2400 = 0.005 m³
Volume (V = l × w × h) #
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Q: Calculate the volume of a rectangular box with length 3 m, width 2 m, and height 4 m.
V = l × w × h = 3 × 2 × 4 = 24 m³
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Q: A cube has sides of length 5 cm. What is its volume in cm³?
V = l × w × h = 5 × 5 × 5 = 125 cm³
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Q: A rectangular tank is 2 m long and 1.5 m wide. What height must it be to hold 9 m³?
h = V/(l × w) = 9/(2 × 1.5) = 3 m
Pressure (P = F/A) #
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Q: A force of 500 N acts on an area of 2.5 m². Calculate the pressure.
P = F/A = 500/2.5 = 200 Pa
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Q: What force is needed to create a pressure of 40 Pa on an area of 0.5 m²?
F = P × A = 40 × 0.5 = 20 N
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Q: A pressure of 100 Pa is created by a force of 250 N. What is the area?
A = F/P = 250/100 = 2.5 m²
Work Done (W = F × d) #
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Q: Calculate the work done when a force of 150 N moves an object 3 meters.
W = F × d = 150 × 3 = 450 J
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Q: How far does a 40 N force move an object to do 200 J of work?
d = W/F = 200/40 = 5 m
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Q: What force is needed to do 300 J of work over a distance of 15 meters?
F = W/d = 300/15 = 20 N
Kinetic Energy (KE = ½mv²) #
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Q: Calculate the kinetic energy of a 4 kg object moving at 3 m/s.
KE = ½mv² = ½ × 4 × 3² = ½ × 4 × 9 = 18 J
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Q: A 1000 kg car has kinetic energy of 200,000 J. Calculate its speed.
v = √(2 × KE/m) = √(2 × 200,000/1000) = √400 = 20 m/s
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Q: What is the mass of an object with kinetic energy 450 J when moving at 10 m/s?
m = (2 × KE)/v² = (2 × 450)/100 = 9 kg
