PHYS 112- SL Midterm #2 Review

To accelerate as quickly as possible in a car from a stopped position, you would

• Brake as hard as you can

• Press down very lightly on the gas pedal so that your car’s wheels turn with gradually increasing acceleration, so the static force of friction propels you forward

• Press the gas pedal down as quickly as you can without spinning your wheels in place so the static force of friction propels you forward

• None of the above, since the force of friction cannot provide a forward force on a car.

True or False?

If F_applied = f_s you will be able to get an object at rest to slip.

• True

• False

Which of the following statements about terminal velocity are true? Select all that apply.

• At terminal velocity, the net acceleration of the object is 0.

• At terminal velocity, the magnitude of the drag force is equal to the magnitude of the weight.

• At terminal velocity, the object is massless.

• Terminal velocity is achieved at the highest point of motion.

• Terminal velocity is inversely proportional to the square root of the cross-sectional area.

An object slides down a frictionless slope.  Which of the following equations correctly shows the net force in the y-direction?

• ΣF_y= n-Wsin55°

• ΣF_y= n-Wcos55°

• ΣF_y= Wsin55°-n

• ΣF_y= n-Wcos55°-n

• ΣF_y= n-W

A mass m is swung in a horizontal circle from a 5 m long rope which is suspended from the ceiling as shown in the figure. The rope makes a 20° angle with the vertical axis. Find the magnitude of the angular velocity of the mass.

• Impossible to determine without knowing m.

• 0.84 rad/s

• 0.71 rad/s

• 1.44 rad/s

• 2.1 rad/s

True or False? All objects undergoing uniform circular motion travel with a constant velocity.

• True

• False

A 1 m radius solid object that increases in angular velocity from ω_1z=5 rad/s to ω_2z=10 rad/s in a 5 second interval has an average angular acceleration, α_z, of

• 1 rad/s²

• 25 rad/s²

• -1 rad/s²

• 1 m/s²

• -1 m/s²

Which force would be most effective in giving the rod the largest negative torque?

• F₁

• F₂

• F₃

• F₄

• F₅

True or False?

A crumpled ball of paper that is falling to the ground experiences a greater drag force than a flat sheet of paper floating face-down from the same height.

• True

• False

A ladder leans up against a wall and is not slipping.  Which of the following diagrams correctly shows the forces acting on the ladder?

• 
• 
• 
• 
• None of the above