Problem Solving

MOTION WITH CONSTANT ACCELERATION

1.    Entering the Freeway. A car sits in an entrance ramp to a freeway, waiting for a break in the traffic. The driver accelerates with constant acceleration along the ramp and onto the freeway. The car starts from rest, moves in a straight line, and has a speed of 20 m/s when it reaches the end of the 120-m-long ramp.

a.    What is the acceleration of the car?

b.    How much time does it take the car to travel the length of the ramp?

c.    The traffic on the freeway is moving at a constant speed of 20m/s. What distance does the traffic travel while the car is moving the length of the ramp?

FREE-FALL

1.    A tennis ball on Mars, where the acceleration due to gravity is 0.379g and air resistance is negligible, is hit directly upward and returns to the same level 8.5 s later.

a.    How high above its original point did the ball go?

b.    How fast was it moving just after being hit?

c.    Sketch graphs of the balls vertical position, vertical velocity, and vertical acceleration as functions of time while its in the Martian air.

PROJECTILE MOTION

1.    Two crickets, Chirpy and Milada, jump from the top of a vertical cliff. Chirpy just drops and reaches the ground in 3.50 s, while Milada jumps horizontally with an initial speed of 95.0 cm/s How far from the base of the cliff will Milada hit the ground?

CIRCULAR MOTION

1.    A model of a helicopter rotor has four blades, each 3.40 m long from the central shaft to the blade tip. The model is rotated in a wind tunnel at 550rev/min.

a.    What is the linear speed of the blade tip

b.    What is the radial acceleration of the blade tip expressed as a multiple of the acceleration of gravity, g?

APPLICATION OF NEWTONS LAW

1.    Workmen are trying to free an SUV stuck in the mud. To extricate the vehicle, they use three horizontal ropes, producing the force vectors shown in Fig. E4.2.

a.    Find the x- and y-components of each of the three pulls.

b.    Use the components to find the magnitude and direction of the resultant of the three pulls

2.    A man is dragging a trunk up the loading ramp of a movers truck. The ramp has a slope angle of 20 and the man pulls upward with a force whose direction makes an angle of with the ramp (Fig. E4.4).

a.    How large a force is necessary for the component parallel to the ramp to be 60.0 N?

b.    How large will the component perpendicular to the ramp then be?