A 0.025 kg golf ball moving at 18.0 m/s crashes through the window of a house in 5.0 × 10-4 s. After the crash, the ball continues in the same direction with a speed of 10.0 m/s. Assuming the force exerted on the ball by the window was constant, what was the magnitude of this force? What impulse was delivered to the ball?
400 Newtons of Force and .2 kg · m/s of Impulse
1. Finding the Force Exerted on the Ball
Step | Formula Derivation | Reasoning |
---|---|---|
1 | F = \frac{\Delta p}{\Delta t} | Force (F) is the change in momentum (\Delta p) over time (\Delta t). |
2 | \Delta p = m(v_f – v_i) | Change in momentum, where m is mass, v_f is final velocity, and v_i is initial velocity. |
3 | \Delta t = 5.0 \times 10^{-4}, \text{s} | Time duration of the crash. |
4 | F = \frac{0.025, \text{kg} \times (10.0, \text{m/s} – 18.0, \text{m/s})}{5.0 \times 10^{-4}, \text{s}} | Substituting values to calculate the force. |
2. Finding the Impulse Delivered to the Ball
Step | Formula Derivation | Reasoning |
---|---|---|
1 | J = \Delta p | Impulse (J) is the change in momentum. |
2 | J = m(v_f – v_i) | Substituting the formula for change in momentum. |
Let’s calculate the magnitude of the force and the impulse.
A space probe far from the Earth is traveling at 14.8 km/s. It has mass 1312 kg. The probe fires its rockets to give a constant thrust of 156 kN for 220 seconds. It accelerates in the same direction as its initial velocity. In this time it burns 150 kg of fuel. Calculate final speed of the space probe in km/s.
Note: This is a bonus question. Skip if you haven’t yet taken calculus.
400 Newtons of Force and .2 kg · m/s of Impulse
Home » A 0.025 kg golf ball moving at 18.0 m/s crashes through the window of a house in 5.0 × 10-4 s. After the crash, the ball continues in the same direction with a speed of 10.0 m/s. Assuming the force exerted on the ball by the window was constant, what was the magnitude of this force? What impulse was delivered to the ball?
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Kinematics | Forces |
---|---|
\Delta x = v_i \cdot t + \frac{1}{2} a \cdot t^2 | F = m \cdot a |
v = v_i + a \cdot t | F_g = \frac{G \cdot m_1 \cdot m_2}{r^2} |
a = \frac{\Delta v}{\Delta t} | f = \mu \cdot N |
R = \frac{v_i^2 \cdot \sin(2\theta)}{g} |
Circular Motion | Energy |
---|---|
F_c = \frac{m \cdot v^2}{r} | KE = \frac{1}{2} m \cdot v^2 |
a_c = \frac{v^2}{r} | PE = m \cdot g \cdot h |
KE_i + PE_i = KE_f + PE_f |
Momentum | Torque and Rotations |
---|---|
p = m \cdot v | \tau = r \cdot F \cdot \sin(\theta) |
J = \Delta p | I = \sum m \cdot r^2 |
p_i = p_f | L = I \cdot \omega |
Simple Harmonic Motion |
---|
F = -k \cdot x |
T = 2\pi \sqrt{\frac{l}{g}} |
T = 2\pi \sqrt{\frac{m}{k}} |
Constant | Description |
---|---|
g | Acceleration due to gravity, typically 9.8 , \text{m/s}^2 on Earth’s surface |
G | Universal Gravitational Constant, 6.674 \times 10^{-11} , \text{N} \cdot \text{m}^2/\text{kg}^2 |
\mu_k and \mu_s | Coefficients of kinetic (\mu_k) and static (\mu_s) friction, dimensionless. Static friction (\mu_s) is usually greater than kinetic friction (\mu_k) as it resists the start of motion. |
k | Spring constant, in \text{N/m} |
Variable | SI Unit |
---|---|
s (Displacement) | \text{meters (m)} |
v (Velocity) | \text{meters per second (m/s)} |
a (Acceleration) | \text{meters per second squared (m/s}^2\text{)} |
t (Time) | \text{seconds (s)} |
m (Mass) | \text{kilograms (kg)} |
Variable | Derived SI Unit |
---|---|
F (Force) | \text{newtons (N)} |
E, PE, KE (Energy, Potential Energy, Kinetic Energy) | \text{joules (J)} |
P (Power) | \text{watts (W)} |
p (Momentum) | \text{kilogram meters per second (kg·m/s)} |
\omega (Angular Velocity) | \text{radians per second (rad/s)} |
\tau (Torque) | \text{newton meters (N·m)} |
I (Moment of Inertia) | \text{kilogram meter squared (kg·m}^2\text{)} |
f (Frequency) | \text{hertz (Hz)} |
General Metric Conversion Chart
Example of using unit analysis: Convert 5 kilometers to millimeters.
Start with the given measurement: \text{5 km}
Use the conversion factors for kilometers to meters and meters to millimeters: \text{5 km} \times \frac{10^3 \, \text{m}}{1 \, \text{km}} \times \frac{10^3 \, \text{mm}}{1 \, \text{m}}
Perform the multiplication: \text{5 km} \times \frac{10^3 \, \text{m}}{1 \, \text{km}} \times \frac{10^3 \, \text{mm}}{1 \, \text{m}} = 5 \times 10^3 \times 10^3 \, \text{mm}
Simplify to get the final answer: \boxed{5 \times 10^6 \, \text{mm}}
Prefix | Symbol | Power of Ten | Equivalent |
---|---|---|---|
Pico- | p | 10^{-12} | 0.000000000001 |
Nano- | n | 10^{-9} | 0.000000001 |
Micro- | µ | 10^{-6} | 0.000001 |
Milli- | m | 10^{-3} | 0.001 |
Centi- | c | 10^{-2} | 0.01 |
Deci- | d | 10^{-1} | 0.1 |
(Base unit) | – | 10^{0} | 1 |
Deca- or Deka- | da | 10^{1} | 10 |
Hecto- | h | 10^{2} | 100 |
Kilo- | k | 10^{3} | 1,000 |
Mega- | M | 10^{6} | 1,000,000 |
Giga- | G | 10^{9} | 1,000,000,000 |
Tera- | T | 10^{12} | 1,000,000,000,000 |