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Physics 8A Summer 2003 Midterm 1 1. (15 pts) A man exerts a steady force of 25.0 N on a block of mass 2.0 kg as he pushes it up a 30° incline. The incline is 15.0 m long. The block starts out Stationary at the bottom of the incline, which is on the ground. (a) What is the speed of the block when it reaches the top of the incline? Assume the surface is frictionless. (b) Once the block reaches the top, the man lets go of it and allows it to travel freely through the air until it hits the ground. How much total time does the object spend on its trip (ie, the time from when it starts at the bottom of the incline until it lands on the ground)? 2. (10 pts) A man walks 5.0 kph (kilometers per hour) for 10.0 minutes at 30° north of east, then 3.0 kph for 15.0 minutes at 20° east of south. Find the average velocity (magnitude and direction) for the trip. 3. (10 pts) In the diagram, m, = 3.0 kg and m, = 4.0 kg. The block m, is falling with an acceleration of 1.60 m/s’. Find the coefficient of kinetic friction between the block m, and the surface of the incline. OM -» L 4. (15 pts) Suppose we have a conical pendulum as pictured here. This one is different from the one shown in lecture; instead of the string having its other end attached to a hanging mass, it’s attached directly to the top of a pole. The mass m we) shown is 0.50 kg. The mass travels around in a horizontal m circle with a radius of 25.0 cm, and its speed is 3.0 m/s. Find 2E.C om the angle 8, and the tension in the string. 
