Question

7. When an object undergoes uniform circular motion, the direction of the acceleration is a. directed tangent to the circle b. directed toward the centre of the circle c. changing depending on its position in the circle d. directed outward from the centre of the circle e. opposite to the direction of centripetal force car travels with a constant speed around a curve in the road. The curve is banked Which of the following forces is in the direction of the net force on the car? a. the x-component of the force of gravity b. the frictional force C, the x-component of the normal force d. the force of gravity e the centrifugal force 9. A spring with a force constant of 150.0 Nm was stretched 5.7 cm. The work done to stretch the spring was a. 0.24 J b. 8.6 J С. 430 J d. 860 J e. 2400 J 10. If the mass of a car is tripled and its speed is doubled, then the kinetic energy changes by a factor of. a. 0.67 b. 1.5 c. 6 d. 12 e. 18 11. If done long enough, rubbing two sticks together can produce enough heat to start a fire. If 100.0 J of thermal energy is required to start the fire and the average frictional force between the sticks is 20.0 N, the distance the sticks must slide past one other is: a. 2.00 m b. 5.00 m C. 10.0 m d. 100.0 m e. 2.00 x 10m To catch a water-filled balloon without breaking it, people allow their hands to move with the balloon upon catching it. This works because: a the balloon's momentum changes more slowly b. there is less force applied c there is less impulse d, two of A, B, and C e. all of A, B, and C 12.

Answer 1

An object experiences a uniform circular motion, the direction of centripetal acceleration is acts towords the center of circle Therefore, option (b)is correct A car is moving uniform speed on a banked curve, resolve Normal reacxtion (N) into components, vertical component balances the weight(N cos theta = mg) of the car Net force acting on the car is equal to centrifugal force acts towords center of circle. F_net = F_centri = N sin theta Therefore, option (e) is correct Expression for work done in stretching the spring is, W = 1/2 k x^2 = 1/2 (150 N/m) (0.057 m)^2 = 0.24 J Therefore, option (a) is correct Final Kinetic energy changed by a factor is, K E_f x = 1/ 2 (3 m) (2 v)^2 = 12 [1/ 2 m v^2] Therefore, option (d) is correct From work-energy theorem work done is equal to change in kinetic energy. W = delta K E = F delta x