MCAT Physics Practice Questions

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Which of the following statements correctly identifies an example of the respective scalar or vector product processes? I. Vector and scalar : torque II. Vector and vector : magnetic force III. Sca ... lar and scalar : power III only I only II and III I and II - ANSWER II and III A scalar multiplied by a scalar will produce another scalar. For instance, distance divided by time is equal to speed, which is a scalar. In the case of power, energy divided by time is equal to power. Statement III is true. A vector multiplied by a scalar is representative of the scalar product or the dot product and will always produce a vector. The scalar product of two vectors A and B can be constructed by taking the component of A in the direction of B and multiplying it times the magnitude of B, and it can be expressed as ABcosθ. Torque is not an example of the scalar product of vectors since it is equal to rFsinθ. A correct example of the dot product would be work, which is equal to Fdcosθ. Therefore, statement I is not true. Vector multiplied by a vector is representative of the vector product or the cross product and will produce a vector or scalar. The magnitude of the vector product of A and B can be constructed by taking the product of the magnitudes of A and B multiplied by the sine of the angle between them. Magnetic force is an example of the vector cross product, so statement II is true. Therefore, the correct answer is that statements II and III are true. Which of the following is a true statement concerning speed, velocity, and acceleration? A. If the displacement of an object is zero, the speed must be zero B. An increase in speed must mean the object experiences acceleration C. Speed is a vector quantity representing magnitude and direction D. An object cannot accelerate if it is moving at a constant speed - ANSWER The vector quantity representing magnitude and direction is velocity, not speed Because speed is not a vector quantity, constant speed cannot tell us direction of an object. Therefore you can move at constant speed but still accelerate by changing direction. Displacement of an object could equal zero simply by moving in a circle. If your initial and final positions are the same, your displacement is zero but your speed is not. An object can only experience an increase in speed if it is accelerated An elevator's motion is through the action of a single cable. The elevator has a gravitational force of 2000 N. When the elevator is moving downwards at a constant velocity, how much tension is in this cable? equal to 2000 N slightly less than 2000 N greater than 2000 N close to 0 N - ANSWER equal to 2000N Drawing a free-body diagram of a elevator in motion will elucidate the forces on the elevator The forces on the elevator when it is moving downwards at a constant velocity are the gravitational force and the force due to the tension on the cable. If the elevator is moving at constant velocity, then there is no net acceleration and no net force. The tension in the cable must equal the gravitational force of the elevator. For a three second period of time, a 50 kg wooden crate slides across the concrete floor at exactly 5 m/s. The coefficient of kinetic friction between the wooden crate and the concrete floor is 0.2. What is the net force of this crate during this three second period? 500 N 50 N [Show More]

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