# phy 108 questions 4

Chapter 5 Circular motion, the planets and gravity

- A ball is traveling at a constant speed of 5 m/s in a circle with a radius of 0.8 m. What is the centripetal acceleration of the ball? Whatâ€™s its direction?
- A car with a mass of 1200 kg is moving around a curve with a radius of 40 m at a constant speed of 20 m/s.

a) What is the centripetal acceleration of the car?

b) What is the magnitude of the force required to produce this centripetal acceleration? - Two 100-kg persons are separated by a distance of 1 m. using Newtonâ€™s law of gravitation, find the magnitude of the attractive gravitational force exerted by one person to the other.
- Two masses are attracted by a gravitational force of 0.36 N. What will the force of attraction be if the distance between the two masses is tripled?
- Does an astronaut have the same weight in different planets? Explain why.
- Why uniform circular motion has acceleration if it has the same speed everywhere?