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Option 1: Just fill in the form with your homework question, and someone will respond shortly with an answer.

Option 2: Take a photo (or link) of your question, and email or text it to us.

Like us? Vertical Motion of a Rocket

Q: A rocket moves upward, starting from rest with an acceleration of 27.2 m/s2 for 3.49 s. It runs out of fuel at the end of the 3.49 s, but does not stop. How high does it rise above the ground?

A: Okay the rocket’s moving up with an acceleration of +27.2m/s^2 for a . . . → Read More: Vertical Motion of a Rocket

Tips to Remember for Kinematics and Projectile Questions

Some things you should know for projectiles (note that you haven’t done anything with angles yet, so you can ignore the sine and cosine parts):

The vertical and horizontal components are independent of each other. The vertical velocity is usually Vy = V*sin(ϴ) horizontal velocity is usually Vx = V*cos(ϴ), where V is the . . . → Read More: Tips to Remember for Kinematics and Projectile Questions

Cart Collision in 1-Dimension

Q: Two carts with masses of 4.6 kg and 3.5 kg move toward each other on a frictionless track with speeds of 5.7 m/s and 4.5 m/s, respectively. The carts stick together after colliding head-on. Find their final speed.

A: m1 = 4.6 kg m2 = 3.5 kg v1 = 5.7 m/s (to the . . . → Read More: Cart Collision in 1-Dimension

Kinetic energy of racing car

Q: A racing car has a mass of 1780 kg. The acceleration of gravity is 9.8 m/s^2. What is its kinetic energy if it has a speed of 103 km/h?

A: First note that kinetic energy can be denoted as KE or E_k[\latex]= 728550 J E_k[\latex] = 7.3×10^5 J

Gravity doesn’t affect the kinetic . . . → Read More: Kinetic energy of racing car

Scooter and Bicycle, when will they meet?

Q: At 8:00am Dave leaves his home on his scooter, traveling east at 18 mph. At the same time and 80 mile away, Cathy leaves her home on her bicycle, traveling west toward Dave at 14 mph. At what time will they meet?

A: You know that D=VT, where D=distance, V=velocity (speed) and T . . . → Read More: Scooter and Bicycle, when will they meet?

An arrow is shot off a cliff at an angle, with crosswind

Q: A student standing on the top of a cliff shoots an arrow from a height of 30.0 m at 25.0 m/s and an initial angle of 32.0° above the horizontal. There are four parts to this question.

a) What will be the horizontal and vertical components of the arrow’s initial speed?

Horizontal component . . . → Read More: An arrow is shot off a cliff at an angle, with crosswind

Friction Force

Friction force is usually denoted with Ff. The coefficient of friction is defined by , (pronounced mu) and is a property of the material that the object rests on. For instance, a smooth wooden coffee table would have a much lower value for than a piece of sandpaper, for example.

The formula for friction . . . → Read More: Friction Force

Find friction force, given mass and coefficient of friction

Q: The coefficient of static friction between a book and the level surface it slides on is 0.65. If the mass of the book is 2.0 kg, what minimum initial applied force is required to slide the books across the surface?

A: State what you know.

= 0.65 m = 2.0 kg g . . . → Read More: Find friction force, given mass and coefficient of friction

Find coefficient of friction, given force and mass

Q: An engine provides 5.0 kN of force to keep a 1600-kg vehicle moving at a uniform speed. (Air resistance is negligible.) What is the coefficient of rolling friction between the tires and the road surface?

A: First convert 5.0 kN to Newtons: F = 5.0 kN = 5000 N. (Just like 5 kg . . . → Read More: Find coefficient of friction, given force and mass